deffunc H_{1}( 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 = H_{1}(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

consider f being sequence of (El_Filtration (t,MyFunc)) such that

A1: for d being Element of NAT holds f . d = H

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