deffunc H_{1}( Nat) -> Element of NAT = DigitDC2 (x,$1,k);

consider z being FinSequence of NAT such that

A1: len z = n and

A2: for j being Nat st j in dom z holds

z . j = H_{1}(j)
from FINSEQ_2:sch 1();

A3: dom z = Seg n by A1, FINSEQ_1:def 3;

reconsider z = z as Tuple of n, NAT by A1, CARD_1:def 7;

take z ; :: thesis: for i being Nat st i in Seg n holds

z . i = DigitDC2 (x,i,k)

let i be Nat; :: thesis: ( i in Seg n implies z . i = DigitDC2 (x,i,k) )

assume i in Seg n ; :: thesis: z . i = DigitDC2 (x,i,k)

hence z . i = DigitDC2 (x,i,k) by A2, A3; :: thesis: verum

consider z being FinSequence of NAT such that

A1: len z = n and

A2: for j being Nat st j in dom z holds

z . j = H

A3: dom z = Seg n by A1, FINSEQ_1:def 3;

reconsider z = z as Tuple of n, NAT by A1, CARD_1:def 7;

take z ; :: thesis: for i being Nat st i in Seg n holds

z . i = DigitDC2 (x,i,k)

let i be Nat; :: thesis: ( i in Seg n implies z . i = DigitDC2 (x,i,k) )

assume i in Seg n ; :: thesis: z . i = DigitDC2 (x,i,k)

hence z . i = DigitDC2 (x,i,k) by A2, A3; :: thesis: verum