reserve x, x1, x2, y, X, D for set,
  i, j, k, l, m, n, N for Nat,
  p, q for XFinSequence of NAT,
  q9 for XFinSequence,
  pd, qd for XFinSequence of D;

theorem Th30:
  card Domin_0(2+k,1) = k+1
proof
  card Domin_0(2+k,1)=(2+k+1-2*1)/(2+k+1-1)*((2+k) choose 1) by Th29,NAT_1:11
    .=(k+1)/(2+k)*(2+k) by STIRL2_1:51
    .=k+1 by XCMPLX_1:87;
  hence thesis;
end;
