| Step | Hyp | Ref | Expression | 
						
							| 1 |  | nfseq.1 | ⊢ Ⅎ 𝑥 𝑀 | 
						
							| 2 |  | nfseq.2 | ⊢ Ⅎ 𝑥  + | 
						
							| 3 |  | nfseq.3 | ⊢ Ⅎ 𝑥 𝐹 | 
						
							| 4 |  | df-seq | ⊢ seq 𝑀 (  +  ,  𝐹 )  =  ( rec ( ( 𝑧  ∈  V ,  𝑤  ∈  V  ↦  〈 ( 𝑧  +  1 ) ,  ( 𝑤  +  ( 𝐹 ‘ ( 𝑧  +  1 ) ) ) 〉 ) ,  〈 𝑀 ,  ( 𝐹 ‘ 𝑀 ) 〉 )  “  ω ) | 
						
							| 5 |  | nfcv | ⊢ Ⅎ 𝑥 V | 
						
							| 6 |  | nfcv | ⊢ Ⅎ 𝑥 ( 𝑧  +  1 ) | 
						
							| 7 |  | nfcv | ⊢ Ⅎ 𝑥 𝑤 | 
						
							| 8 | 3 6 | nffv | ⊢ Ⅎ 𝑥 ( 𝐹 ‘ ( 𝑧  +  1 ) ) | 
						
							| 9 | 7 2 8 | nfov | ⊢ Ⅎ 𝑥 ( 𝑤  +  ( 𝐹 ‘ ( 𝑧  +  1 ) ) ) | 
						
							| 10 | 6 9 | nfop | ⊢ Ⅎ 𝑥 〈 ( 𝑧  +  1 ) ,  ( 𝑤  +  ( 𝐹 ‘ ( 𝑧  +  1 ) ) ) 〉 | 
						
							| 11 | 5 5 10 | nfmpo | ⊢ Ⅎ 𝑥 ( 𝑧  ∈  V ,  𝑤  ∈  V  ↦  〈 ( 𝑧  +  1 ) ,  ( 𝑤  +  ( 𝐹 ‘ ( 𝑧  +  1 ) ) ) 〉 ) | 
						
							| 12 | 3 1 | nffv | ⊢ Ⅎ 𝑥 ( 𝐹 ‘ 𝑀 ) | 
						
							| 13 | 1 12 | nfop | ⊢ Ⅎ 𝑥 〈 𝑀 ,  ( 𝐹 ‘ 𝑀 ) 〉 | 
						
							| 14 | 11 13 | nfrdg | ⊢ Ⅎ 𝑥 rec ( ( 𝑧  ∈  V ,  𝑤  ∈  V  ↦  〈 ( 𝑧  +  1 ) ,  ( 𝑤  +  ( 𝐹 ‘ ( 𝑧  +  1 ) ) ) 〉 ) ,  〈 𝑀 ,  ( 𝐹 ‘ 𝑀 ) 〉 ) | 
						
							| 15 |  | nfcv | ⊢ Ⅎ 𝑥 ω | 
						
							| 16 | 14 15 | nfima | ⊢ Ⅎ 𝑥 ( rec ( ( 𝑧  ∈  V ,  𝑤  ∈  V  ↦  〈 ( 𝑧  +  1 ) ,  ( 𝑤  +  ( 𝐹 ‘ ( 𝑧  +  1 ) ) ) 〉 ) ,  〈 𝑀 ,  ( 𝐹 ‘ 𝑀 ) 〉 )  “  ω ) | 
						
							| 17 | 4 16 | nfcxfr | ⊢ Ⅎ 𝑥 seq 𝑀 (  +  ,  𝐹 ) |