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

theorem
  51 satisfies_Sierpinski_problem_76b
  proof
    let x be Nat;
    assume 10*51 < x < 10*(51+1);
    then 510 < x < 519+1;
    then 510+1 <= x <= 519 by NAT_1:13;
    then x = 511 or ... or x = 519;
    hence thesis by XPRIMES0:511,512,513,514,515,516,517,518,519;
  end;
