deffunc H₁( Element of NAT ) -> Element of K10(X) = A \ (A1 . $1);
ex f being SetSequence of X st
for n being Element of NAT holds f . n = H₁(n) from FUNCT_2:sch 4();
hence ex b₁ being SetSequence of X st
for n being Element of NAT holds b₁ . n = A \ (A1 . n) ; :: thesis: verum