| Step | Hyp | Ref | Expression | 
						
							| 1 |  | simpl | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  𝐴  ∈  ω ) | 
						
							| 2 |  | nnon | ⊢ ( 𝐴  ∈  ω  →  𝐴  ∈  On ) | 
						
							| 3 | 1 2 | syl | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  𝐴  ∈  On ) | 
						
							| 4 |  | omelon | ⊢ ω  ∈  On | 
						
							| 5 |  | limom | ⊢ Lim  ω | 
						
							| 6 | 4 5 | pm3.2i | ⊢ ( ω  ∈  On  ∧  Lim  ω ) | 
						
							| 7 | 6 | a1i | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  ( ω  ∈  On  ∧  Lim  ω ) ) | 
						
							| 8 |  | 0elon | ⊢ ∅  ∈  On | 
						
							| 9 | 8 | a1i | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  ∅  ∈  On ) | 
						
							| 10 |  | 0ss | ⊢ ∅  ⊆  1o | 
						
							| 11 | 10 | a1i | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  ∅  ⊆  1o ) | 
						
							| 12 |  | simpr | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  1o  ∈  𝐴 ) | 
						
							| 13 |  | ontr2 | ⊢ ( ( ∅  ∈  On  ∧  𝐴  ∈  On )  →  ( ( ∅  ⊆  1o  ∧  1o  ∈  𝐴 )  →  ∅  ∈  𝐴 ) ) | 
						
							| 14 | 13 | imp | ⊢ ( ( ( ∅  ∈  On  ∧  𝐴  ∈  On )  ∧  ( ∅  ⊆  1o  ∧  1o  ∈  𝐴 ) )  →  ∅  ∈  𝐴 ) | 
						
							| 15 | 9 3 11 12 14 | syl22anc | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  ∅  ∈  𝐴 ) | 
						
							| 16 |  | oelim | ⊢ ( ( ( 𝐴  ∈  On  ∧  ( ω  ∈  On  ∧  Lim  ω ) )  ∧  ∅  ∈  𝐴 )  →  ( 𝐴  ↑o  ω )  =  ∪  𝑥  ∈  ω ( 𝐴  ↑o  𝑥 ) ) | 
						
							| 17 | 3 7 15 16 | syl21anc | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  ( 𝐴  ↑o  ω )  =  ∪  𝑥  ∈  ω ( 𝐴  ↑o  𝑥 ) ) | 
						
							| 18 |  | ovex | ⊢ ( 𝐴  ↑o  𝑥 )  ∈  V | 
						
							| 19 | 18 | dfiun2 | ⊢ ∪  𝑥  ∈  ω ( 𝐴  ↑o  𝑥 )  =  ∪  { 𝑦  ∣  ∃ 𝑥  ∈  ω 𝑦  =  ( 𝐴  ↑o  𝑥 ) } | 
						
							| 20 |  | eluniab | ⊢ ( 𝑧  ∈  ∪  { 𝑦  ∣  ∃ 𝑥  ∈  ω 𝑦  =  ( 𝐴  ↑o  𝑥 ) }  ↔  ∃ 𝑦 ( 𝑧  ∈  𝑦  ∧  ∃ 𝑥  ∈  ω 𝑦  =  ( 𝐴  ↑o  𝑥 ) ) ) | 
						
							| 21 |  | 19.42v | ⊢ ( ∃ 𝑥 ( 𝑧  ∈  𝑦  ∧  ( 𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) )  ↔  ( 𝑧  ∈  𝑦  ∧  ∃ 𝑥 ( 𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) ) ) | 
						
							| 22 |  | 3anass | ⊢ ( ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) )  ↔  ( 𝑧  ∈  𝑦  ∧  ( 𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) ) ) | 
						
							| 23 | 22 | exbii | ⊢ ( ∃ 𝑥 ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) )  ↔  ∃ 𝑥 ( 𝑧  ∈  𝑦  ∧  ( 𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) ) ) | 
						
							| 24 |  | df-rex | ⊢ ( ∃ 𝑥  ∈  ω 𝑦  =  ( 𝐴  ↑o  𝑥 )  ↔  ∃ 𝑥 ( 𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) ) | 
						
							| 25 | 24 | anbi2i | ⊢ ( ( 𝑧  ∈  𝑦  ∧  ∃ 𝑥  ∈  ω 𝑦  =  ( 𝐴  ↑o  𝑥 ) )  ↔  ( 𝑧  ∈  𝑦  ∧  ∃ 𝑥 ( 𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) ) ) | 
						
							| 26 | 21 23 25 | 3bitr4ri | ⊢ ( ( 𝑧  ∈  𝑦  ∧  ∃ 𝑥  ∈  ω 𝑦  =  ( 𝐴  ↑o  𝑥 ) )  ↔  ∃ 𝑥 ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) ) | 
						
							| 27 | 26 | exbii | ⊢ ( ∃ 𝑦 ( 𝑧  ∈  𝑦  ∧  ∃ 𝑥  ∈  ω 𝑦  =  ( 𝐴  ↑o  𝑥 ) )  ↔  ∃ 𝑦 ∃ 𝑥 ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) ) | 
						
							| 28 |  | excom | ⊢ ( ∃ 𝑦 ∃ 𝑥 ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) )  ↔  ∃ 𝑥 ∃ 𝑦 ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) ) | 
						
							| 29 | 20 27 28 | 3bitri | ⊢ ( 𝑧  ∈  ∪  { 𝑦  ∣  ∃ 𝑥  ∈  ω 𝑦  =  ( 𝐴  ↑o  𝑥 ) }  ↔  ∃ 𝑥 ∃ 𝑦 ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) ) | 
						
							| 30 |  | simpr3 | ⊢ ( ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  ∧  ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) )  →  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) | 
						
							| 31 |  | simp2 | ⊢ ( ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) )  →  𝑥  ∈  ω ) | 
						
							| 32 |  | nnecl | ⊢ ( ( 𝐴  ∈  ω  ∧  𝑥  ∈  ω )  →  ( 𝐴  ↑o  𝑥 )  ∈  ω ) | 
						
							| 33 | 1 31 32 | syl2an | ⊢ ( ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  ∧  ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) )  →  ( 𝐴  ↑o  𝑥 )  ∈  ω ) | 
						
							| 34 |  | onelss | ⊢ ( ω  ∈  On  →  ( ( 𝐴  ↑o  𝑥 )  ∈  ω  →  ( 𝐴  ↑o  𝑥 )  ⊆  ω ) ) | 
						
							| 35 | 4 33 34 | mpsyl | ⊢ ( ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  ∧  ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) )  →  ( 𝐴  ↑o  𝑥 )  ⊆  ω ) | 
						
							| 36 | 30 35 | eqsstrd | ⊢ ( ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  ∧  ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) )  →  𝑦  ⊆  ω ) | 
						
							| 37 |  | simpr1 | ⊢ ( ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  ∧  ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) )  →  𝑧  ∈  𝑦 ) | 
						
							| 38 | 36 37 | sseldd | ⊢ ( ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  ∧  ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) )  →  𝑧  ∈  ω ) | 
						
							| 39 | 38 | ex | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  ( ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) )  →  𝑧  ∈  ω ) ) | 
						
							| 40 | 39 | exlimdvv | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  ( ∃ 𝑥 ∃ 𝑦 ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) )  →  𝑧  ∈  ω ) ) | 
						
							| 41 |  | peano2 | ⊢ ( 𝑧  ∈  ω  →  suc  𝑧  ∈  ω ) | 
						
							| 42 | 41 | adantl | ⊢ ( ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  ∧  𝑧  ∈  ω )  →  suc  𝑧  ∈  ω ) | 
						
							| 43 |  | ovex | ⊢ ( 𝐴  ↑o  suc  𝑧 )  ∈  V | 
						
							| 44 | 43 | a1i | ⊢ ( ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  ∧  𝑧  ∈  ω )  →  ( 𝐴  ↑o  suc  𝑧 )  ∈  V ) | 
						
							| 45 | 2 | anim1i | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  ( 𝐴  ∈  On  ∧  1o  ∈  𝐴 ) ) | 
						
							| 46 |  | ondif2 | ⊢ ( 𝐴  ∈  ( On  ∖  2o )  ↔  ( 𝐴  ∈  On  ∧  1o  ∈  𝐴 ) ) | 
						
							| 47 | 45 46 | sylibr | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  𝐴  ∈  ( On  ∖  2o ) ) | 
						
							| 48 |  | nnon | ⊢ ( suc  𝑧  ∈  ω  →  suc  𝑧  ∈  On ) | 
						
							| 49 | 41 48 | syl | ⊢ ( 𝑧  ∈  ω  →  suc  𝑧  ∈  On ) | 
						
							| 50 |  | oeworde | ⊢ ( ( 𝐴  ∈  ( On  ∖  2o )  ∧  suc  𝑧  ∈  On )  →  suc  𝑧  ⊆  ( 𝐴  ↑o  suc  𝑧 ) ) | 
						
							| 51 | 47 49 50 | syl2an | ⊢ ( ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  ∧  𝑧  ∈  ω )  →  suc  𝑧  ⊆  ( 𝐴  ↑o  suc  𝑧 ) ) | 
						
							| 52 |  | vex | ⊢ 𝑧  ∈  V | 
						
							| 53 | 52 | sucid | ⊢ 𝑧  ∈  suc  𝑧 | 
						
							| 54 | 53 | a1i | ⊢ ( ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  ∧  𝑧  ∈  ω )  →  𝑧  ∈  suc  𝑧 ) | 
						
							| 55 | 51 54 | sseldd | ⊢ ( ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  ∧  𝑧  ∈  ω )  →  𝑧  ∈  ( 𝐴  ↑o  suc  𝑧 ) ) | 
						
							| 56 |  | eqidd | ⊢ ( ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  ∧  𝑧  ∈  ω )  →  ( 𝐴  ↑o  suc  𝑧 )  =  ( 𝐴  ↑o  suc  𝑧 ) ) | 
						
							| 57 | 55 42 56 | 3jca | ⊢ ( ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  ∧  𝑧  ∈  ω )  →  ( 𝑧  ∈  ( 𝐴  ↑o  suc  𝑧 )  ∧  suc  𝑧  ∈  ω  ∧  ( 𝐴  ↑o  suc  𝑧 )  =  ( 𝐴  ↑o  suc  𝑧 ) ) ) | 
						
							| 58 |  | eleq2 | ⊢ ( 𝑦  =  ( 𝐴  ↑o  suc  𝑧 )  →  ( 𝑧  ∈  𝑦  ↔  𝑧  ∈  ( 𝐴  ↑o  suc  𝑧 ) ) ) | 
						
							| 59 |  | eqeq1 | ⊢ ( 𝑦  =  ( 𝐴  ↑o  suc  𝑧 )  →  ( 𝑦  =  ( 𝐴  ↑o  suc  𝑧 )  ↔  ( 𝐴  ↑o  suc  𝑧 )  =  ( 𝐴  ↑o  suc  𝑧 ) ) ) | 
						
							| 60 | 58 59 | 3anbi13d | ⊢ ( 𝑦  =  ( 𝐴  ↑o  suc  𝑧 )  →  ( ( 𝑧  ∈  𝑦  ∧  suc  𝑧  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  suc  𝑧 ) )  ↔  ( 𝑧  ∈  ( 𝐴  ↑o  suc  𝑧 )  ∧  suc  𝑧  ∈  ω  ∧  ( 𝐴  ↑o  suc  𝑧 )  =  ( 𝐴  ↑o  suc  𝑧 ) ) ) ) | 
						
							| 61 | 44 57 60 | spcedv | ⊢ ( ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  ∧  𝑧  ∈  ω )  →  ∃ 𝑦 ( 𝑧  ∈  𝑦  ∧  suc  𝑧  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  suc  𝑧 ) ) ) | 
						
							| 62 |  | eleq1 | ⊢ ( 𝑥  =  suc  𝑧  →  ( 𝑥  ∈  ω  ↔  suc  𝑧  ∈  ω ) ) | 
						
							| 63 |  | oveq2 | ⊢ ( 𝑥  =  suc  𝑧  →  ( 𝐴  ↑o  𝑥 )  =  ( 𝐴  ↑o  suc  𝑧 ) ) | 
						
							| 64 | 63 | eqeq2d | ⊢ ( 𝑥  =  suc  𝑧  →  ( 𝑦  =  ( 𝐴  ↑o  𝑥 )  ↔  𝑦  =  ( 𝐴  ↑o  suc  𝑧 ) ) ) | 
						
							| 65 | 62 64 | 3anbi23d | ⊢ ( 𝑥  =  suc  𝑧  →  ( ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) )  ↔  ( 𝑧  ∈  𝑦  ∧  suc  𝑧  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  suc  𝑧 ) ) ) ) | 
						
							| 66 | 65 | exbidv | ⊢ ( 𝑥  =  suc  𝑧  →  ( ∃ 𝑦 ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) )  ↔  ∃ 𝑦 ( 𝑧  ∈  𝑦  ∧  suc  𝑧  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  suc  𝑧 ) ) ) ) | 
						
							| 67 | 42 61 66 | spcedv | ⊢ ( ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  ∧  𝑧  ∈  ω )  →  ∃ 𝑥 ∃ 𝑦 ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) ) | 
						
							| 68 | 67 | ex | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  ( 𝑧  ∈  ω  →  ∃ 𝑥 ∃ 𝑦 ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) ) ) ) | 
						
							| 69 | 40 68 | impbid | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  ( ∃ 𝑥 ∃ 𝑦 ( 𝑧  ∈  𝑦  ∧  𝑥  ∈  ω  ∧  𝑦  =  ( 𝐴  ↑o  𝑥 ) )  ↔  𝑧  ∈  ω ) ) | 
						
							| 70 | 29 69 | bitrid | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  ( 𝑧  ∈  ∪  { 𝑦  ∣  ∃ 𝑥  ∈  ω 𝑦  =  ( 𝐴  ↑o  𝑥 ) }  ↔  𝑧  ∈  ω ) ) | 
						
							| 71 | 70 | eqrdv | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  ∪  { 𝑦  ∣  ∃ 𝑥  ∈  ω 𝑦  =  ( 𝐴  ↑o  𝑥 ) }  =  ω ) | 
						
							| 72 | 19 71 | eqtrid | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  ∪  𝑥  ∈  ω ( 𝐴  ↑o  𝑥 )  =  ω ) | 
						
							| 73 | 17 72 | eqtrd | ⊢ ( ( 𝐴  ∈  ω  ∧  1o  ∈  𝐴 )  →  ( 𝐴  ↑o  ω )  =  ω ) |