%I #18 Aug 20 2023 11:44:36

%S 1,3,10,63,147,156,225,234,408,600,680,684,952,1014,1496,1500,1768,

%T 2176,2584,3128,3944,4216,4224,4275,5032,5576,5848,5880,6392,6498,

%U 6660,6875,7208,8024,8296,8379,9112,9324,9656,9840,9928

%N Numbers k such that k / (A000005(k)*(A000005(k)+1)/2) is an integer.

%H Amiram Eldar, <a href="/A160921/b160921.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..136 from R. J. Mathar)

%p n :=1 :

%p for k from 1 to 50000 do

%p if modp (k,A184389(k)) = 0 then

%p printf("%d %d\n",n,k) ;

%p n := n+1 ;

%p end if;

%p end do: # _R. J. Mathar_, Oct 04 2014

%t t[n_] := n*(n + 1)/2; Select[Range[10^4], Divisible[#, t[DivisorSigma[0, #]]] &] (* _Amiram Eldar_, Jan 17 2021 *)

%t dsiQ[n_]:=With[{d=DivisorSigma[0,n]},IntegerQ[n/((d(d+1))/2)]]; Select[Range[10000],dsiQ] (* _Harvey P. Dale_, Aug 20 2023 *)

%o (PARI) lista(nn) = {for (n=1, nn, if (2*n % (numdiv(n)*(numdiv(n)+1)) == 0, print1(n, ", ")););} \\ _Michel Marcus_, Jun 02 2013

%Y Cf. A000005, A033950.

%K easy,nonn

%O 1,2

%A _Ctibor O. Zizka_, May 30 2009

%E Corrected by _Michel Marcus_, Jun 02 2013