This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A180490 #19 Jan 10 2025 10:09:37
%S A180490 1,2,4,8,12,16,20,24,32,36,40,48,64,68,72,80,81,96,128,132,136,144,
%T A180490 160,162,192,240,252,256,260,261,264,272,288,320,324,368,384,425,432,
%U A180490 464,480,504,512,516,520,522,528,544,576,624,625,637,640,648,675,688,720
%N A180490 Numbers k such that (A000120(k))^2 divides k.
%C A180490 This is a subsequence of A049445.
%H A180490 Alois P. Heinz, <a href="/A180490/b180490.txt">Table of n, a(n) for n = 1..10000</a>
%F A180490 {k: (A000120(k))^2 | k}.
%t A180490 fQ[n_] := Divisible[ n, DigitCount[n, 2, 1]^2]; Select[ Range@ 735, fQ] (* _Robert G. Wilson v_, Sep 10 2010 *)
%o A180490 (PARI) isok(k) = !(k % hammingweight(k)^2); \\ _Amiram Eldar_, Jan 10 2025
%o A180490 (Python)
%o A180490 def ok(n): return n and n%n.bit_count()**2 == 0
%o A180490 print([k for k in range(721) if ok(k)]) # _Michael S. Branicky_, Jan 10 2025
%Y A180490 Cf. A000120, A049445.
%K A180490 easy,nonn,base
%O A180490 1,2
%A A180490 _Ctibor O. Zizka_, Sep 08 2010
%E A180490 a(43) onwards from _Robert G. Wilson v_, Sep 10 2010