| Step | Hyp | Ref | Expression | 
						
							| 1 |  | simp3 |  |-  ( ( S C_ CC /\ F e. ( CC ^pm S ) /\ N e. NN0 ) -> N e. NN0 ) | 
						
							| 2 |  | nn0uz |  |-  NN0 = ( ZZ>= ` 0 ) | 
						
							| 3 | 1 2 | eleqtrdi |  |-  ( ( S C_ CC /\ F e. ( CC ^pm S ) /\ N e. NN0 ) -> N e. ( ZZ>= ` 0 ) ) | 
						
							| 4 |  | seqp1 |  |-  ( N e. ( ZZ>= ` 0 ) -> ( seq 0 ( ( ( x e. _V |-> ( S _D x ) ) o. 1st ) , ( NN0 X. { F } ) ) ` ( N + 1 ) ) = ( ( seq 0 ( ( ( x e. _V |-> ( S _D x ) ) o. 1st ) , ( NN0 X. { F } ) ) ` N ) ( ( x e. _V |-> ( S _D x ) ) o. 1st ) ( ( NN0 X. { F } ) ` ( N + 1 ) ) ) ) | 
						
							| 5 | 3 4 | syl |  |-  ( ( S C_ CC /\ F e. ( CC ^pm S ) /\ N e. NN0 ) -> ( seq 0 ( ( ( x e. _V |-> ( S _D x ) ) o. 1st ) , ( NN0 X. { F } ) ) ` ( N + 1 ) ) = ( ( seq 0 ( ( ( x e. _V |-> ( S _D x ) ) o. 1st ) , ( NN0 X. { F } ) ) ` N ) ( ( x e. _V |-> ( S _D x ) ) o. 1st ) ( ( NN0 X. { F } ) ` ( N + 1 ) ) ) ) | 
						
							| 6 |  | fvex |  |-  ( seq 0 ( ( ( x e. _V |-> ( S _D x ) ) o. 1st ) , ( NN0 X. { F } ) ) ` N ) e. _V | 
						
							| 7 |  | fvex |  |-  ( ( NN0 X. { F } ) ` ( N + 1 ) ) e. _V | 
						
							| 8 | 6 7 | opco1i |  |-  ( ( seq 0 ( ( ( x e. _V |-> ( S _D x ) ) o. 1st ) , ( NN0 X. { F } ) ) ` N ) ( ( x e. _V |-> ( S _D x ) ) o. 1st ) ( ( NN0 X. { F } ) ` ( N + 1 ) ) ) = ( ( x e. _V |-> ( S _D x ) ) ` ( seq 0 ( ( ( x e. _V |-> ( S _D x ) ) o. 1st ) , ( NN0 X. { F } ) ) ` N ) ) | 
						
							| 9 | 5 8 | eqtrdi |  |-  ( ( S C_ CC /\ F e. ( CC ^pm S ) /\ N e. NN0 ) -> ( seq 0 ( ( ( x e. _V |-> ( S _D x ) ) o. 1st ) , ( NN0 X. { F } ) ) ` ( N + 1 ) ) = ( ( x e. _V |-> ( S _D x ) ) ` ( seq 0 ( ( ( x e. _V |-> ( S _D x ) ) o. 1st ) , ( NN0 X. { F } ) ) ` N ) ) ) | 
						
							| 10 |  | eqid |  |-  ( x e. _V |-> ( S _D x ) ) = ( x e. _V |-> ( S _D x ) ) | 
						
							| 11 | 10 | dvnfval |  |-  ( ( S C_ CC /\ F e. ( CC ^pm S ) ) -> ( S Dn F ) = seq 0 ( ( ( x e. _V |-> ( S _D x ) ) o. 1st ) , ( NN0 X. { F } ) ) ) | 
						
							| 12 | 11 | 3adant3 |  |-  ( ( S C_ CC /\ F e. ( CC ^pm S ) /\ N e. NN0 ) -> ( S Dn F ) = seq 0 ( ( ( x e. _V |-> ( S _D x ) ) o. 1st ) , ( NN0 X. { F } ) ) ) | 
						
							| 13 | 12 | fveq1d |  |-  ( ( S C_ CC /\ F e. ( CC ^pm S ) /\ N e. NN0 ) -> ( ( S Dn F ) ` ( N + 1 ) ) = ( seq 0 ( ( ( x e. _V |-> ( S _D x ) ) o. 1st ) , ( NN0 X. { F } ) ) ` ( N + 1 ) ) ) | 
						
							| 14 |  | fvex |  |-  ( ( S Dn F ) ` N ) e. _V | 
						
							| 15 |  | oveq2 |  |-  ( x = ( ( S Dn F ) ` N ) -> ( S _D x ) = ( S _D ( ( S Dn F ) ` N ) ) ) | 
						
							| 16 |  | ovex |  |-  ( S _D ( ( S Dn F ) ` N ) ) e. _V | 
						
							| 17 | 15 10 16 | fvmpt |  |-  ( ( ( S Dn F ) ` N ) e. _V -> ( ( x e. _V |-> ( S _D x ) ) ` ( ( S Dn F ) ` N ) ) = ( S _D ( ( S Dn F ) ` N ) ) ) | 
						
							| 18 | 14 17 | ax-mp |  |-  ( ( x e. _V |-> ( S _D x ) ) ` ( ( S Dn F ) ` N ) ) = ( S _D ( ( S Dn F ) ` N ) ) | 
						
							| 19 | 12 | fveq1d |  |-  ( ( S C_ CC /\ F e. ( CC ^pm S ) /\ N e. NN0 ) -> ( ( S Dn F ) ` N ) = ( seq 0 ( ( ( x e. _V |-> ( S _D x ) ) o. 1st ) , ( NN0 X. { F } ) ) ` N ) ) | 
						
							| 20 | 19 | fveq2d |  |-  ( ( S C_ CC /\ F e. ( CC ^pm S ) /\ N e. NN0 ) -> ( ( x e. _V |-> ( S _D x ) ) ` ( ( S Dn F ) ` N ) ) = ( ( x e. _V |-> ( S _D x ) ) ` ( seq 0 ( ( ( x e. _V |-> ( S _D x ) ) o. 1st ) , ( NN0 X. { F } ) ) ` N ) ) ) | 
						
							| 21 | 18 20 | eqtr3id |  |-  ( ( S C_ CC /\ F e. ( CC ^pm S ) /\ N e. NN0 ) -> ( S _D ( ( S Dn F ) ` N ) ) = ( ( x e. _V |-> ( S _D x ) ) ` ( seq 0 ( ( ( x e. _V |-> ( S _D x ) ) o. 1st ) , ( NN0 X. { F } ) ) ` N ) ) ) | 
						
							| 22 | 9 13 21 | 3eqtr4d |  |-  ( ( S C_ CC /\ F e. ( CC ^pm S ) /\ N e. NN0 ) -> ( ( S Dn F ) ` ( N + 1 ) ) = ( S _D ( ( S Dn F ) ` N ) ) ) |