| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							bnj150.1 | 
							⊢ ( 𝜑  ↔  ( 𝑓 ‘ ∅ )  =   pred ( 𝑥 ,  𝐴 ,  𝑅 ) )  | 
						
						
							| 2 | 
							
								
							 | 
							bnj150.2 | 
							⊢ ( 𝜓  ↔  ∀ 𝑖  ∈  ω ( suc  𝑖  ∈  𝑛  →  ( 𝑓 ‘ suc  𝑖 )  =  ∪  𝑦  ∈  ( 𝑓 ‘ 𝑖 )  pred ( 𝑦 ,  𝐴 ,  𝑅 ) ) )  | 
						
						
							| 3 | 
							
								
							 | 
							bnj150.3 | 
							⊢ ( 𝜁  ↔  ( ( 𝑅  FrSe  𝐴  ∧  𝑥  ∈  𝐴 )  →  ( 𝑓  Fn  𝑛  ∧  𝜑  ∧  𝜓 ) ) )  | 
						
						
							| 4 | 
							
								
							 | 
							bnj150.4 | 
							⊢ ( 𝜑′  ↔  [ 1o  /  𝑛 ] 𝜑 )  | 
						
						
							| 5 | 
							
								
							 | 
							bnj150.5 | 
							⊢ ( 𝜓′  ↔  [ 1o  /  𝑛 ] 𝜓 )  | 
						
						
							| 6 | 
							
								
							 | 
							bnj150.6 | 
							⊢ ( 𝜃0  ↔  ( ( 𝑅  FrSe  𝐴  ∧  𝑥  ∈  𝐴 )  →  ∃ 𝑓 ( 𝑓  Fn  1o  ∧  𝜑′  ∧  𝜓′ ) ) )  | 
						
						
							| 7 | 
							
								
							 | 
							bnj150.7 | 
							⊢ ( 𝜁′  ↔  [ 1o  /  𝑛 ] 𝜁 )  | 
						
						
							| 8 | 
							
								
							 | 
							bnj150.8 | 
							⊢ 𝐹  =  { 〈 ∅ ,   pred ( 𝑥 ,  𝐴 ,  𝑅 ) 〉 }  | 
						
						
							| 9 | 
							
								
							 | 
							bnj150.9 | 
							⊢ ( 𝜑″  ↔  [ 𝐹  /  𝑓 ] 𝜑′ )  | 
						
						
							| 10 | 
							
								
							 | 
							bnj150.10 | 
							⊢ ( 𝜓″  ↔  [ 𝐹  /  𝑓 ] 𝜓′ )  | 
						
						
							| 11 | 
							
								
							 | 
							bnj150.11 | 
							⊢ ( 𝜁″  ↔  [ 𝐹  /  𝑓 ] 𝜁′ )  | 
						
						
							| 12 | 
							
								8
							 | 
							bnj95 | 
							⊢ 𝐹  ∈  V  | 
						
						
							| 13 | 
							
								
							 | 
							sbceq1a | 
							⊢ ( 𝑓  =  𝐹  →  ( 𝜁′  ↔  [ 𝐹  /  𝑓 ] 𝜁′ ) )  | 
						
						
							| 14 | 
							
								13 11
							 | 
							bitr4di | 
							⊢ ( 𝑓  =  𝐹  →  ( 𝜁′  ↔  𝜁″ ) )  | 
						
						
							| 15 | 
							
								
							 | 
							0ex | 
							⊢ ∅  ∈  V  | 
						
						
							| 16 | 
							
								
							 | 
							bnj93 | 
							⊢ ( ( 𝑅  FrSe  𝐴  ∧  𝑥  ∈  𝐴 )  →   pred ( 𝑥 ,  𝐴 ,  𝑅 )  ∈  V )  | 
						
						
							| 17 | 
							
								
							 | 
							funsng | 
							⊢ ( ( ∅  ∈  V  ∧   pred ( 𝑥 ,  𝐴 ,  𝑅 )  ∈  V )  →  Fun  { 〈 ∅ ,   pred ( 𝑥 ,  𝐴 ,  𝑅 ) 〉 } )  | 
						
						
							| 18 | 
							
								15 16 17
							 | 
							sylancr | 
							⊢ ( ( 𝑅  FrSe  𝐴  ∧  𝑥  ∈  𝐴 )  →  Fun  { 〈 ∅ ,   pred ( 𝑥 ,  𝐴 ,  𝑅 ) 〉 } )  | 
						
						
							| 19 | 
							
								8
							 | 
							funeqi | 
							⊢ ( Fun  𝐹  ↔  Fun  { 〈 ∅ ,   pred ( 𝑥 ,  𝐴 ,  𝑅 ) 〉 } )  | 
						
						
							| 20 | 
							
								18 19
							 | 
							sylibr | 
							⊢ ( ( 𝑅  FrSe  𝐴  ∧  𝑥  ∈  𝐴 )  →  Fun  𝐹 )  | 
						
						
							| 21 | 
							
								8
							 | 
							bnj96 | 
							⊢ ( ( 𝑅  FrSe  𝐴  ∧  𝑥  ∈  𝐴 )  →  dom  𝐹  =  1o )  | 
						
						
							| 22 | 
							
								20 21
							 | 
							bnj1422 | 
							⊢ ( ( 𝑅  FrSe  𝐴  ∧  𝑥  ∈  𝐴 )  →  𝐹  Fn  1o )  | 
						
						
							| 23 | 
							
								8
							 | 
							bnj97 | 
							⊢ ( ( 𝑅  FrSe  𝐴  ∧  𝑥  ∈  𝐴 )  →  ( 𝐹 ‘ ∅ )  =   pred ( 𝑥 ,  𝐴 ,  𝑅 ) )  | 
						
						
							| 24 | 
							
								1 4 9 8
							 | 
							bnj125 | 
							⊢ ( 𝜑″  ↔  ( 𝐹 ‘ ∅ )  =   pred ( 𝑥 ,  𝐴 ,  𝑅 ) )  | 
						
						
							| 25 | 
							
								23 24
							 | 
							sylibr | 
							⊢ ( ( 𝑅  FrSe  𝐴  ∧  𝑥  ∈  𝐴 )  →  𝜑″ )  | 
						
						
							| 26 | 
							
								22 25
							 | 
							jca | 
							⊢ ( ( 𝑅  FrSe  𝐴  ∧  𝑥  ∈  𝐴 )  →  ( 𝐹  Fn  1o  ∧  𝜑″ ) )  | 
						
						
							| 27 | 
							
								
							 | 
							bnj98 | 
							⊢ ∀ 𝑖  ∈  ω ( suc  𝑖  ∈  1o  →  ( 𝐹 ‘ suc  𝑖 )  =  ∪  𝑦  ∈  ( 𝐹 ‘ 𝑖 )  pred ( 𝑦 ,  𝐴 ,  𝑅 ) )  | 
						
						
							| 28 | 
							
								2 5 10 8
							 | 
							bnj126 | 
							⊢ ( 𝜓″  ↔  ∀ 𝑖  ∈  ω ( suc  𝑖  ∈  1o  →  ( 𝐹 ‘ suc  𝑖 )  =  ∪  𝑦  ∈  ( 𝐹 ‘ 𝑖 )  pred ( 𝑦 ,  𝐴 ,  𝑅 ) ) )  | 
						
						
							| 29 | 
							
								27 28
							 | 
							mpbir | 
							⊢ 𝜓″  | 
						
						
							| 30 | 
							
								
							 | 
							df-3an | 
							⊢ ( ( 𝐹  Fn  1o  ∧  𝜑″  ∧  𝜓″ )  ↔  ( ( 𝐹  Fn  1o  ∧  𝜑″ )  ∧  𝜓″ ) )  | 
						
						
							| 31 | 
							
								26 29 30
							 | 
							sylanblrc | 
							⊢ ( ( 𝑅  FrSe  𝐴  ∧  𝑥  ∈  𝐴 )  →  ( 𝐹  Fn  1o  ∧  𝜑″  ∧  𝜓″ ) )  | 
						
						
							| 32 | 
							
								3 7 4 5
							 | 
							bnj121 | 
							⊢ ( 𝜁′  ↔  ( ( 𝑅  FrSe  𝐴  ∧  𝑥  ∈  𝐴 )  →  ( 𝑓  Fn  1o  ∧  𝜑′  ∧  𝜓′ ) ) )  | 
						
						
							| 33 | 
							
								8 9 10 11 32
							 | 
							bnj124 | 
							⊢ ( 𝜁″  ↔  ( ( 𝑅  FrSe  𝐴  ∧  𝑥  ∈  𝐴 )  →  ( 𝐹  Fn  1o  ∧  𝜑″  ∧  𝜓″ ) ) )  | 
						
						
							| 34 | 
							
								31 33
							 | 
							mpbir | 
							⊢ 𝜁″  | 
						
						
							| 35 | 
							
								12 14 34
							 | 
							ceqsexv2d | 
							⊢ ∃ 𝑓 𝜁′  | 
						
						
							| 36 | 
							
								
							 | 
							19.37v | 
							⊢ ( ∃ 𝑓 ( ( 𝑅  FrSe  𝐴  ∧  𝑥  ∈  𝐴 )  →  ( 𝑓  Fn  1o  ∧  𝜑′  ∧  𝜓′ ) )  ↔  ( ( 𝑅  FrSe  𝐴  ∧  𝑥  ∈  𝐴 )  →  ∃ 𝑓 ( 𝑓  Fn  1o  ∧  𝜑′  ∧  𝜓′ ) ) )  | 
						
						
							| 37 | 
							
								6 36
							 | 
							bitr4i | 
							⊢ ( 𝜃0  ↔  ∃ 𝑓 ( ( 𝑅  FrSe  𝐴  ∧  𝑥  ∈  𝐴 )  →  ( 𝑓  Fn  1o  ∧  𝜑′  ∧  𝜓′ ) ) )  | 
						
						
							| 38 | 
							
								37 32
							 | 
							bnj133 | 
							⊢ ( 𝜃0  ↔  ∃ 𝑓 𝜁′ )  | 
						
						
							| 39 | 
							
								35 38
							 | 
							mpbir | 
							⊢ 𝜃0  |