| Step | Hyp | Ref | Expression | 
						
							| 1 |  | sseqval.1 |  |-  ( ph -> S e. _V ) | 
						
							| 2 |  | sseqval.2 |  |-  ( ph -> M e. Word S ) | 
						
							| 3 |  | sseqval.3 |  |-  W = ( Word S i^i ( `' # " ( ZZ>= ` ( # ` M ) ) ) ) | 
						
							| 4 |  | sseqval.4 |  |-  ( ph -> F : W --> S ) | 
						
							| 5 |  | df-sseq |  |-  seqstr = ( m e. _V , f e. _V |-> ( m u. ( lastS o. seq ( # ` m ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( f ` x ) "> ) ) , ( NN0 X. { ( m ++ <" ( f ` m ) "> ) } ) ) ) ) ) | 
						
							| 6 | 5 | a1i |  |-  ( ph -> seqstr = ( m e. _V , f e. _V |-> ( m u. ( lastS o. seq ( # ` m ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( f ` x ) "> ) ) , ( NN0 X. { ( m ++ <" ( f ` m ) "> ) } ) ) ) ) ) ) | 
						
							| 7 |  | simprl |  |-  ( ( ph /\ ( m = M /\ f = F ) ) -> m = M ) | 
						
							| 8 | 7 | fveq2d |  |-  ( ( ph /\ ( m = M /\ f = F ) ) -> ( # ` m ) = ( # ` M ) ) | 
						
							| 9 |  | simp1rr |  |-  ( ( ( ph /\ ( m = M /\ f = F ) ) /\ x e. _V /\ y e. _V ) -> f = F ) | 
						
							| 10 | 9 | fveq1d |  |-  ( ( ( ph /\ ( m = M /\ f = F ) ) /\ x e. _V /\ y e. _V ) -> ( f ` x ) = ( F ` x ) ) | 
						
							| 11 | 10 | s1eqd |  |-  ( ( ( ph /\ ( m = M /\ f = F ) ) /\ x e. _V /\ y e. _V ) -> <" ( f ` x ) "> = <" ( F ` x ) "> ) | 
						
							| 12 | 11 | oveq2d |  |-  ( ( ( ph /\ ( m = M /\ f = F ) ) /\ x e. _V /\ y e. _V ) -> ( x ++ <" ( f ` x ) "> ) = ( x ++ <" ( F ` x ) "> ) ) | 
						
							| 13 | 12 | mpoeq3dva |  |-  ( ( ph /\ ( m = M /\ f = F ) ) -> ( x e. _V , y e. _V |-> ( x ++ <" ( f ` x ) "> ) ) = ( x e. _V , y e. _V |-> ( x ++ <" ( F ` x ) "> ) ) ) | 
						
							| 14 |  | simprr |  |-  ( ( ph /\ ( m = M /\ f = F ) ) -> f = F ) | 
						
							| 15 | 14 7 | fveq12d |  |-  ( ( ph /\ ( m = M /\ f = F ) ) -> ( f ` m ) = ( F ` M ) ) | 
						
							| 16 | 15 | s1eqd |  |-  ( ( ph /\ ( m = M /\ f = F ) ) -> <" ( f ` m ) "> = <" ( F ` M ) "> ) | 
						
							| 17 | 7 16 | oveq12d |  |-  ( ( ph /\ ( m = M /\ f = F ) ) -> ( m ++ <" ( f ` m ) "> ) = ( M ++ <" ( F ` M ) "> ) ) | 
						
							| 18 | 17 | sneqd |  |-  ( ( ph /\ ( m = M /\ f = F ) ) -> { ( m ++ <" ( f ` m ) "> ) } = { ( M ++ <" ( F ` M ) "> ) } ) | 
						
							| 19 | 18 | xpeq2d |  |-  ( ( ph /\ ( m = M /\ f = F ) ) -> ( NN0 X. { ( m ++ <" ( f ` m ) "> ) } ) = ( NN0 X. { ( M ++ <" ( F ` M ) "> ) } ) ) | 
						
							| 20 | 8 13 19 | seqeq123d |  |-  ( ( ph /\ ( m = M /\ f = F ) ) -> seq ( # ` m ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( f ` x ) "> ) ) , ( NN0 X. { ( m ++ <" ( f ` m ) "> ) } ) ) = seq ( # ` M ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( F ` x ) "> ) ) , ( NN0 X. { ( M ++ <" ( F ` M ) "> ) } ) ) ) | 
						
							| 21 | 20 | coeq2d |  |-  ( ( ph /\ ( m = M /\ f = F ) ) -> ( lastS o. seq ( # ` m ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( f ` x ) "> ) ) , ( NN0 X. { ( m ++ <" ( f ` m ) "> ) } ) ) ) = ( lastS o. seq ( # ` M ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( F ` x ) "> ) ) , ( NN0 X. { ( M ++ <" ( F ` M ) "> ) } ) ) ) ) | 
						
							| 22 | 7 21 | uneq12d |  |-  ( ( ph /\ ( m = M /\ f = F ) ) -> ( m u. ( lastS o. seq ( # ` m ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( f ` x ) "> ) ) , ( NN0 X. { ( m ++ <" ( f ` m ) "> ) } ) ) ) ) = ( M u. ( lastS o. seq ( # ` M ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( F ` x ) "> ) ) , ( NN0 X. { ( M ++ <" ( F ` M ) "> ) } ) ) ) ) ) | 
						
							| 23 |  | elex |  |-  ( M e. Word S -> M e. _V ) | 
						
							| 24 | 2 23 | syl |  |-  ( ph -> M e. _V ) | 
						
							| 25 |  | wrdexg |  |-  ( S e. _V -> Word S e. _V ) | 
						
							| 26 |  | inex1g |  |-  ( Word S e. _V -> ( Word S i^i ( `' # " ( ZZ>= ` ( # ` M ) ) ) ) e. _V ) | 
						
							| 27 | 1 25 26 | 3syl |  |-  ( ph -> ( Word S i^i ( `' # " ( ZZ>= ` ( # ` M ) ) ) ) e. _V ) | 
						
							| 28 | 3 27 | eqeltrid |  |-  ( ph -> W e. _V ) | 
						
							| 29 | 4 28 | fexd |  |-  ( ph -> F e. _V ) | 
						
							| 30 |  | df-lsw |  |-  lastS = ( x e. _V |-> ( x ` ( ( # ` x ) - 1 ) ) ) | 
						
							| 31 | 30 | funmpt2 |  |-  Fun lastS | 
						
							| 32 | 31 | a1i |  |-  ( ph -> Fun lastS ) | 
						
							| 33 |  | seqex |  |-  seq ( # ` M ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( F ` x ) "> ) ) , ( NN0 X. { ( M ++ <" ( F ` M ) "> ) } ) ) e. _V | 
						
							| 34 | 33 | a1i |  |-  ( ph -> seq ( # ` M ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( F ` x ) "> ) ) , ( NN0 X. { ( M ++ <" ( F ` M ) "> ) } ) ) e. _V ) | 
						
							| 35 |  | cofunexg |  |-  ( ( Fun lastS /\ seq ( # ` M ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( F ` x ) "> ) ) , ( NN0 X. { ( M ++ <" ( F ` M ) "> ) } ) ) e. _V ) -> ( lastS o. seq ( # ` M ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( F ` x ) "> ) ) , ( NN0 X. { ( M ++ <" ( F ` M ) "> ) } ) ) ) e. _V ) | 
						
							| 36 | 32 34 35 | syl2anc |  |-  ( ph -> ( lastS o. seq ( # ` M ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( F ` x ) "> ) ) , ( NN0 X. { ( M ++ <" ( F ` M ) "> ) } ) ) ) e. _V ) | 
						
							| 37 |  | unexg |  |-  ( ( M e. _V /\ ( lastS o. seq ( # ` M ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( F ` x ) "> ) ) , ( NN0 X. { ( M ++ <" ( F ` M ) "> ) } ) ) ) e. _V ) -> ( M u. ( lastS o. seq ( # ` M ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( F ` x ) "> ) ) , ( NN0 X. { ( M ++ <" ( F ` M ) "> ) } ) ) ) ) e. _V ) | 
						
							| 38 | 24 36 37 | syl2anc |  |-  ( ph -> ( M u. ( lastS o. seq ( # ` M ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( F ` x ) "> ) ) , ( NN0 X. { ( M ++ <" ( F ` M ) "> ) } ) ) ) ) e. _V ) | 
						
							| 39 | 6 22 24 29 38 | ovmpod |  |-  ( ph -> ( M seqstr F ) = ( M u. ( lastS o. seq ( # ` M ) ( ( x e. _V , y e. _V |-> ( x ++ <" ( F ` x ) "> ) ) , ( NN0 X. { ( M ++ <" ( F ` M ) "> ) } ) ) ) ) ) |