| Step | Hyp | Ref | Expression | 
						
							| 1 |  | seqof2.1 | ⊢ ( 𝜑  →  𝐴  ∈  𝑉 ) | 
						
							| 2 |  | seqof2.2 | ⊢ ( 𝜑  →  𝑁  ∈  ( ℤ≥ ‘ 𝑀 ) ) | 
						
							| 3 |  | seqof2.3 | ⊢ ( 𝜑  →  ( 𝑀 ... 𝑁 )  ⊆  𝐵 ) | 
						
							| 4 |  | seqof2.4 | ⊢ ( ( 𝜑  ∧  ( 𝑥  ∈  𝐵  ∧  𝑧  ∈  𝐴 ) )  →  𝑋  ∈  𝑊 ) | 
						
							| 5 |  | nfv | ⊢ Ⅎ 𝑥 ( 𝜑  ∧  𝑛  ∈  ( 𝑀 ... 𝑁 ) ) | 
						
							| 6 |  | nffvmpt1 | ⊢ Ⅎ 𝑥 ( ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) ‘ 𝑛 ) | 
						
							| 7 |  | nfcv | ⊢ Ⅎ 𝑥 𝐴 | 
						
							| 8 |  | nffvmpt1 | ⊢ Ⅎ 𝑥 ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑛 ) | 
						
							| 9 | 7 8 | nfmpt | ⊢ Ⅎ 𝑥 ( 𝑧  ∈  𝐴  ↦  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑛 ) ) | 
						
							| 10 | 6 9 | nfeq | ⊢ Ⅎ 𝑥 ( ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) ‘ 𝑛 )  =  ( 𝑧  ∈  𝐴  ↦  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑛 ) ) | 
						
							| 11 | 5 10 | nfim | ⊢ Ⅎ 𝑥 ( ( 𝜑  ∧  𝑛  ∈  ( 𝑀 ... 𝑁 ) )  →  ( ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) ‘ 𝑛 )  =  ( 𝑧  ∈  𝐴  ↦  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑛 ) ) ) | 
						
							| 12 |  | eleq1w | ⊢ ( 𝑥  =  𝑛  →  ( 𝑥  ∈  ( 𝑀 ... 𝑁 )  ↔  𝑛  ∈  ( 𝑀 ... 𝑁 ) ) ) | 
						
							| 13 | 12 | anbi2d | ⊢ ( 𝑥  =  𝑛  →  ( ( 𝜑  ∧  𝑥  ∈  ( 𝑀 ... 𝑁 ) )  ↔  ( 𝜑  ∧  𝑛  ∈  ( 𝑀 ... 𝑁 ) ) ) ) | 
						
							| 14 |  | fveq2 | ⊢ ( 𝑥  =  𝑛  →  ( ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) ‘ 𝑥 )  =  ( ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) ‘ 𝑛 ) ) | 
						
							| 15 |  | fveq2 | ⊢ ( 𝑥  =  𝑛  →  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑥 )  =  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑛 ) ) | 
						
							| 16 | 15 | mpteq2dv | ⊢ ( 𝑥  =  𝑛  →  ( 𝑧  ∈  𝐴  ↦  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑥 ) )  =  ( 𝑧  ∈  𝐴  ↦  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑛 ) ) ) | 
						
							| 17 | 14 16 | eqeq12d | ⊢ ( 𝑥  =  𝑛  →  ( ( ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) ‘ 𝑥 )  =  ( 𝑧  ∈  𝐴  ↦  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑥 ) )  ↔  ( ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) ‘ 𝑛 )  =  ( 𝑧  ∈  𝐴  ↦  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑛 ) ) ) ) | 
						
							| 18 | 13 17 | imbi12d | ⊢ ( 𝑥  =  𝑛  →  ( ( ( 𝜑  ∧  𝑥  ∈  ( 𝑀 ... 𝑁 ) )  →  ( ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) ‘ 𝑥 )  =  ( 𝑧  ∈  𝐴  ↦  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑥 ) ) )  ↔  ( ( 𝜑  ∧  𝑛  ∈  ( 𝑀 ... 𝑁 ) )  →  ( ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) ‘ 𝑛 )  =  ( 𝑧  ∈  𝐴  ↦  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑛 ) ) ) ) ) | 
						
							| 19 | 3 | sselda | ⊢ ( ( 𝜑  ∧  𝑥  ∈  ( 𝑀 ... 𝑁 ) )  →  𝑥  ∈  𝐵 ) | 
						
							| 20 | 1 | adantr | ⊢ ( ( 𝜑  ∧  𝑥  ∈  ( 𝑀 ... 𝑁 ) )  →  𝐴  ∈  𝑉 ) | 
						
							| 21 | 20 | mptexd | ⊢ ( ( 𝜑  ∧  𝑥  ∈  ( 𝑀 ... 𝑁 ) )  →  ( 𝑧  ∈  𝐴  ↦  𝑋 )  ∈  V ) | 
						
							| 22 |  | eqid | ⊢ ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) )  =  ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) | 
						
							| 23 | 22 | fvmpt2 | ⊢ ( ( 𝑥  ∈  𝐵  ∧  ( 𝑧  ∈  𝐴  ↦  𝑋 )  ∈  V )  →  ( ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) ‘ 𝑥 )  =  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) | 
						
							| 24 | 19 21 23 | syl2anc | ⊢ ( ( 𝜑  ∧  𝑥  ∈  ( 𝑀 ... 𝑁 ) )  →  ( ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) ‘ 𝑥 )  =  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) | 
						
							| 25 | 19 | adantr | ⊢ ( ( ( 𝜑  ∧  𝑥  ∈  ( 𝑀 ... 𝑁 ) )  ∧  𝑧  ∈  𝐴 )  →  𝑥  ∈  𝐵 ) | 
						
							| 26 |  | simpll | ⊢ ( ( ( 𝜑  ∧  𝑥  ∈  ( 𝑀 ... 𝑁 ) )  ∧  𝑧  ∈  𝐴 )  →  𝜑 ) | 
						
							| 27 |  | simpr | ⊢ ( ( ( 𝜑  ∧  𝑥  ∈  ( 𝑀 ... 𝑁 ) )  ∧  𝑧  ∈  𝐴 )  →  𝑧  ∈  𝐴 ) | 
						
							| 28 | 26 25 27 4 | syl12anc | ⊢ ( ( ( 𝜑  ∧  𝑥  ∈  ( 𝑀 ... 𝑁 ) )  ∧  𝑧  ∈  𝐴 )  →  𝑋  ∈  𝑊 ) | 
						
							| 29 |  | eqid | ⊢ ( 𝑥  ∈  𝐵  ↦  𝑋 )  =  ( 𝑥  ∈  𝐵  ↦  𝑋 ) | 
						
							| 30 | 29 | fvmpt2 | ⊢ ( ( 𝑥  ∈  𝐵  ∧  𝑋  ∈  𝑊 )  →  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑥 )  =  𝑋 ) | 
						
							| 31 | 25 28 30 | syl2anc | ⊢ ( ( ( 𝜑  ∧  𝑥  ∈  ( 𝑀 ... 𝑁 ) )  ∧  𝑧  ∈  𝐴 )  →  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑥 )  =  𝑋 ) | 
						
							| 32 | 31 | mpteq2dva | ⊢ ( ( 𝜑  ∧  𝑥  ∈  ( 𝑀 ... 𝑁 ) )  →  ( 𝑧  ∈  𝐴  ↦  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑥 ) )  =  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) | 
						
							| 33 | 24 32 | eqtr4d | ⊢ ( ( 𝜑  ∧  𝑥  ∈  ( 𝑀 ... 𝑁 ) )  →  ( ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) ‘ 𝑥 )  =  ( 𝑧  ∈  𝐴  ↦  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑥 ) ) ) | 
						
							| 34 | 11 18 33 | chvarfv | ⊢ ( ( 𝜑  ∧  𝑛  ∈  ( 𝑀 ... 𝑁 ) )  →  ( ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) ‘ 𝑛 )  =  ( 𝑧  ∈  𝐴  ↦  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑛 ) ) ) | 
						
							| 35 |  | nfcv | ⊢ Ⅎ 𝑦 ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑛 ) | 
						
							| 36 |  | nfcsb1v | ⊢ Ⅎ 𝑧 ⦋ 𝑦  /  𝑧 ⦌ ( 𝑥  ∈  𝐵  ↦  𝑋 ) | 
						
							| 37 |  | nfcv | ⊢ Ⅎ 𝑧 𝑛 | 
						
							| 38 | 36 37 | nffv | ⊢ Ⅎ 𝑧 ( ⦋ 𝑦  /  𝑧 ⦌ ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑛 ) | 
						
							| 39 |  | csbeq1a | ⊢ ( 𝑧  =  𝑦  →  ( 𝑥  ∈  𝐵  ↦  𝑋 )  =  ⦋ 𝑦  /  𝑧 ⦌ ( 𝑥  ∈  𝐵  ↦  𝑋 ) ) | 
						
							| 40 | 39 | fveq1d | ⊢ ( 𝑧  =  𝑦  →  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑛 )  =  ( ⦋ 𝑦  /  𝑧 ⦌ ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑛 ) ) | 
						
							| 41 | 35 38 40 | cbvmpt | ⊢ ( 𝑧  ∈  𝐴  ↦  ( ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑛 ) )  =  ( 𝑦  ∈  𝐴  ↦  ( ⦋ 𝑦  /  𝑧 ⦌ ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑛 ) ) | 
						
							| 42 | 34 41 | eqtrdi | ⊢ ( ( 𝜑  ∧  𝑛  ∈  ( 𝑀 ... 𝑁 ) )  →  ( ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) ‘ 𝑛 )  =  ( 𝑦  ∈  𝐴  ↦  ( ⦋ 𝑦  /  𝑧 ⦌ ( 𝑥  ∈  𝐵  ↦  𝑋 ) ‘ 𝑛 ) ) ) | 
						
							| 43 | 1 2 42 | seqof | ⊢ ( 𝜑  →  ( seq 𝑀 (  ∘f   +  ,  ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) ) ‘ 𝑁 )  =  ( 𝑦  ∈  𝐴  ↦  ( seq 𝑀 (  +  ,  ⦋ 𝑦  /  𝑧 ⦌ ( 𝑥  ∈  𝐵  ↦  𝑋 ) ) ‘ 𝑁 ) ) ) | 
						
							| 44 |  | nfcv | ⊢ Ⅎ 𝑦 ( seq 𝑀 (  +  ,  ( 𝑥  ∈  𝐵  ↦  𝑋 ) ) ‘ 𝑁 ) | 
						
							| 45 |  | nfcv | ⊢ Ⅎ 𝑧 𝑀 | 
						
							| 46 |  | nfcv | ⊢ Ⅎ 𝑧  + | 
						
							| 47 | 45 46 36 | nfseq | ⊢ Ⅎ 𝑧 seq 𝑀 (  +  ,  ⦋ 𝑦  /  𝑧 ⦌ ( 𝑥  ∈  𝐵  ↦  𝑋 ) ) | 
						
							| 48 |  | nfcv | ⊢ Ⅎ 𝑧 𝑁 | 
						
							| 49 | 47 48 | nffv | ⊢ Ⅎ 𝑧 ( seq 𝑀 (  +  ,  ⦋ 𝑦  /  𝑧 ⦌ ( 𝑥  ∈  𝐵  ↦  𝑋 ) ) ‘ 𝑁 ) | 
						
							| 50 | 39 | seqeq3d | ⊢ ( 𝑧  =  𝑦  →  seq 𝑀 (  +  ,  ( 𝑥  ∈  𝐵  ↦  𝑋 ) )  =  seq 𝑀 (  +  ,  ⦋ 𝑦  /  𝑧 ⦌ ( 𝑥  ∈  𝐵  ↦  𝑋 ) ) ) | 
						
							| 51 | 50 | fveq1d | ⊢ ( 𝑧  =  𝑦  →  ( seq 𝑀 (  +  ,  ( 𝑥  ∈  𝐵  ↦  𝑋 ) ) ‘ 𝑁 )  =  ( seq 𝑀 (  +  ,  ⦋ 𝑦  /  𝑧 ⦌ ( 𝑥  ∈  𝐵  ↦  𝑋 ) ) ‘ 𝑁 ) ) | 
						
							| 52 | 44 49 51 | cbvmpt | ⊢ ( 𝑧  ∈  𝐴  ↦  ( seq 𝑀 (  +  ,  ( 𝑥  ∈  𝐵  ↦  𝑋 ) ) ‘ 𝑁 ) )  =  ( 𝑦  ∈  𝐴  ↦  ( seq 𝑀 (  +  ,  ⦋ 𝑦  /  𝑧 ⦌ ( 𝑥  ∈  𝐵  ↦  𝑋 ) ) ‘ 𝑁 ) ) | 
						
							| 53 | 43 52 | eqtr4di | ⊢ ( 𝜑  →  ( seq 𝑀 (  ∘f   +  ,  ( 𝑥  ∈  𝐵  ↦  ( 𝑧  ∈  𝐴  ↦  𝑋 ) ) ) ‘ 𝑁 )  =  ( 𝑧  ∈  𝐴  ↦  ( seq 𝑀 (  +  ,  ( 𝑥  ∈  𝐵  ↦  𝑋 ) ) ‘ 𝑁 ) ) ) |