reserve i,j,k,n,m,l,s,t for Nat;
reserve a,b for Real;
reserve F for real-valued FinSequence;
reserve z for Complex;
reserve x,y for Complex;
reserve r,s,t for natural Number;

theorem Th15:
  (s+1)! = (s!) * (s+1)
proof
  idseq (s+1) = idseq s ^ <* s+1 *> by FINSEQ_2:51;
  hence thesis by RVSUM_1:96;
end;
