cp's OEIS Frontend

A330708 Numbers that are not the sum of 2 nonzero squares and a positive cube.

%I A330708 #40 Jun 13 2020 00:50:27
%S A330708 0,1,2,4,5,7,8,12,15,17,20,22,23,24,31,36,39,43,50,55,57,63,65,70,71,
%T A330708 78,87,94,103,111,113,115,119,120,134,139,141,148,160,167,169,185,204,
%U A330708 211,254,263,267,279,283,286,302,311,312,331,335,342,349,379,391
%N A330708 Numbers that are not the sum of 2 nonzero squares and a positive cube.
%C A330708 A022552 is a subsequence.
%C A330708 a(490) = A022552(434) = 5042631. No more terms <= 4 * 10^7.
%H A330708 Robert Israel, <a href="/A330708/b330708.txt">Table of n, a(n) for n = 1..490</a>
%p A330708 N:= 500: # for terms <= N
%p A330708 G1:= add(x^(i^2), i=1..floor(sqrt(N))):
%p A330708 G2:= add(x^(i^3), i=1..floor(N^(1/3))):
%p A330708 G:= expand(G1^2*G2):
%p A330708 select(t -> coeff(G,x,t)=0, [$0..N]); # _Robert Israel_, Jun 12 2020
%t A330708 m = 0;
%t A330708 n = 400.;
%t A330708 t = Union@Flatten@Table[x^2 + y^2 + z^3, {x, (n/2)^(1/2)}, {y, x, (n - x^2)^(1/2)}, {z, If[x^2 + y^2 < m, Floor[(m - 1 - x^2 - y^2)^(1/3)] + 1, 1], (n - x^2 - y^2)^(1/3)}];
%t A330708 Complement[Range[m, n], t]
%Y A330708 Cf. A022552, A000534, A004214.
%K A330708 nonn
%O A330708 1,3
%A A330708 _XU Pingya_, Jun 08 2020