cp's OEIS Frontend

A371968 Numbers k that are not the sum of distinct squares that do not divide k.

%I A371968 #24 Apr 16 2024 14:00:38
%S A371968 1,2,3,4,5,6,7,8,9,10,11,12,14,15,16,17,18,19,20,21,22,23,24,26,27,28,
%T A371968 30,31,32,33,35,36,37,39,40,42,43,44,46,47,48,50,51,54,55,56,57,59,60,
%U A371968 63,64,66,67,68,71,72,75,76,79,80,82,84,88,91,92,95,96,99,104,107,108,111,112,120,124,127,128,132,135,140,144,147,148,156,160,168,172,176,184,188,192,200,216,224,252,256,288,300,432
%N A371968 Numbers k that are not the sum of distinct squares that do not divide k.
%C A371968 Numbers k such that A294266(k) = 0.
%C A371968 No other terms <= 100000.
%e A371968 a(20) = 21 is a term because the only way to write 21 as the sum of distinct squares is 1^2 + 2^2 + 4^2, but 21 is divisible by 1^2.
%p A371968 filter:= proc(n) local P,k,x;
%p A371968 P:= 1;
%p A371968 for k from 2 to floor(sqrt(n)) do
%p A371968   if n mod k^2 = 0 then next fi;
%p A371968   P:= series(P*(1+x^(k^2)),x,n+1);
%p A371968   if coeff(P,x,n) > 0 then return false fi;
%p A371968 od;
%p A371968 true
%p A371968 end proc:
%p A371968 select(filter, [$1..500]);
%Y A371968 Cf. A294266.
%K A371968 nonn
%O A371968 1,2
%A A371968 _Robert Israel_, Apr 15 2024
%E A371968 More terms than usual in the DATA section, because these are probably all the terms.