reserve a,b,c,k,m,n for Nat;
reserve i,j for Integer;
reserve p for Prime;

theorem Th14:
  primeindex p < k implies (primesFinS k).(1+primeindex p) = p
  proof
    set i = primeindex p;
    assume i < k;
    then primesFinS k.(i+1) = primenumber i by Def1;
    hence thesis by NUMBER10:def 4;
  end;
