A180490 Numbers k such that (A000120(k))^2 divides k.

1, 2, 4, 8, 12, 16, 20, 24, 32, 36, 40, 48, 64, 68, 72, 80, 81, 96, 128, 132, 136, 144, 160, 162, 192, 240, 252, 256, 260, 261, 264, 272, 288, 320, 324, 368, 384, 425, 432, 464, 480, 504, 512, 516, 520, 522, 528, 544, 576, 624, 625, 637, 640, 648, 675, 688, 720

Offset

1,2

Comments

This is a subsequence of A049445.

Links

Alois P. Heinz, Table of n, a(n) for n = 1..10000

Formula

{k: (A000120(k))^2 | k}.

Mathematica

fQ[n_] := Divisible[ n, DigitCount[n, 2, 1]^2]; Select[ Range@ 735, fQ] (* Robert G. Wilson v, Sep 10 2010 *)

Prog

(PARI) isok(k) = !(k % hammingweight(k)^2); \\ Amiram Eldar, Jan 10 2025
(Python)
def ok(n): return n and n%n.bit_count()**2 == 0
print([k for k in range(721) if ok(k)]) # Michael S. Branicky, Jan 10 2025

Crossrefs

Cf. A000120, A049445.

Sequence in context: A335738 A364056 A010066 * A376616 A160408 A221707

Adjacent sequences: A180487 A180488 A180489 * A180491 A180492 A180493

Keyword

easy,nonn,base

Author

Ctibor O. Zizka, Sep 08 2010

Extensions

a(43) onwards from Robert G. Wilson v, Sep 10 2010

Status

approved