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
  2! = 2
proof
  thus 2! = 1*2 by FINSEQ_2:52,RVSUM_1:99
  .= 2;
end;
