cp's OEIS Frontend

A004440 Numbers that are not the sum of 3 distinct nonzero squares.

%I A004440 #23 Jul 22 2025 13:29:45
%S A004440 1,2,3,4,5,6,7,8,9,10,11,12,13,15,16,17,18,19,20,22,23,24,25,27,28,31,
%T A004440 32,33,34,36,37,39,40,43,44,47,48,51,52,55,57,58,60,63,64,67,68,71,72,
%U A004440 73,76,79,80,82,85,87,88,92,95,96,97,99,100,102,103,108,111,112,119,123,124,127,128,130,132,135,136,143,144,148,151,156,159,160,163,167,172,175,176
%N A004440 Numbers that are not the sum of 3 distinct nonzero squares.
%H A004440 Robert Israel, <a href="/A004440/b004440.txt">Table of n, a(n) for n = 1..10000</a>
%H A004440 <a href="/index/Su#ssq">Index entries for sequences related to sums of squares</a>
%p A004440 N:= 1000: # to get all terms <= N
%p A004440 V:= Vector(N):
%p A004440 for x from 1 to floor(sqrt(N/3)) do
%p A004440   for y from x+1 to floor(sqrt((N-x^2)/2)) do
%p A004440     zs:= [$(y+1).. floor(sqrt(N-x^2-y^2))];
%p A004440     V[map(z -> x^2 + y^2 + z^2, zs)]:= 1;
%p A004440   od
%p A004440 od:
%p A004440 select(i -> V[i] = 0, [$1..N]); # _Robert Israel_, Dec 31 2015
%Y A004440 Cf. A004432 (complement).
%K A004440 nonn
%O A004440 1,2
%A A004440 _N. J. A. Sloane_