reserve a,b,i,k,m,n for Nat;
reserve s,z for non zero Nat;
reserve c for Complex;

theorem Th12:
  k < 961 & n*n <= k & n is prime implies
  n = 2 or n = 3 or n = 5 or n = 7 or n = 11 or n = 13 or n = 17 or n = 19 or
  n = 23 or n = 29
  proof
    assume
A1: k < 961;
    assume that
A2: n*n <= k and
A3: n is prime;
    n*n < 31*31 by A1,A2,XXREAL_0:2;
    hence thesis by A3,Th11,NAT_4:1;
  end;
