deffunc H₁( Nat) -> Element of El_Filtration (t,MyFunc) = Sigma_tauhelp2 (MyFunc,tau,A1,$1,t);
consider f being sequence of (El_Filtration (t,MyFunc)) such that
A1: for d being Element of NAT holds f . d = H₁(d) from FUNCT_2:sch 4();
reconsider f = f as SetSequence of El_Filtration (t,MyFunc) by PROB_4:2;
take f ; :: thesis: for n being Nat holds f . n = Sigma_tauhelp2 (MyFunc,tau,A1,n,t)
let n be Nat; :: thesis: f . n = Sigma_tauhelp2 (MyFunc,tau,A1,n,t)
n in NAT by ORDINAL1:def 12;
hence f . n = Sigma_tauhelp2 (MyFunc,tau,A1,n,t) by A1; :: thesis: verum