%I #15 May 27 2024 09:17:30
%S 1,4,9,16,20,25,30,36,49,64,80,81,90,100,120,121,126,130,144,150,169,
%T 180,195,196,210,225,252,256,264,270,272,280,289,294,300,315,320,324,
%U 330,336,350,360,361,378,390,396,400,414,420,441,450,468,480,484,500
%N Numbers which are sums of squares of some subset of divisors.
%C If m is in the sequence then so is m*k^2 for k >= 1. - _David A. Corneth_, Jan 22 2024
%H David A. Corneth, <a href="/A066213/b066213.txt">Table of n, a(n) for n = 1..10000</a>
%H David A. Corneth, <a href="/A066213/a066213.gp.txt">PARI program</a>
%e 20 is in the list since 20 = 2^2 + 4^2 and 2 and 4 are divisors of 20
%p isA066213 := proc(n)
%p local S,els;
%p S:=subsets(numtheory[divisors](n));
%p while not S[finished] do
%p els:=S[nextvalue]() ;
%p if add(d^2,d=els) = n then
%p return true ;
%p end if ;
%p end do;
%p false
%p end proc:
%p for n from 1 do
%p if isA066213(n) then
%p print(n) ;
%p end if;
%p end do: # _R. J. Mathar_, Oct 09 2023
%t okQ[k_] := AnyTrue[Subsets[Select[Divisors[k]^2, # <= k&]], Total[#]==k&];
%t Reap[For[k = 1, k <= 5000, k++, If[okQ[k], Print[k]; Sow[k]]]][[2, 1]] (* _Jean-François Alcover_, May 27 2024 *)
%o (PARI) \\ See PARI link
%Y Cf. A005835, A066214, A066215, A066216.
%K nonn
%O 1,2
%A _Erich Friedman_, Dec 17 2001
%E Offset 1 from _David A. Corneth_, Jan 22 2024