A068332 Numbers k such that 2^tau(k) <= k < 2*2^tau(k).

5, 7, 9, 21, 22, 26, 27, 68, 75, 76, 92, 98, 99, 116, 117, 124, 258, 266, 273, 282, 285, 286, 290, 296, 297, 310, 318, 322, 328, 344, 345, 351, 354, 357, 366, 370, 374, 375, 376, 385, 399, 402, 406, 410, 418, 424, 426, 429, 430, 434, 435, 438, 442, 455, 459

Offset: 1

Author

Benoit Cloitre, Mar 25 2002

Keywords

• easy
• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000005, A338506.

Programs

Mathematica

q[k_] := Module[{d = DivisorSigma[0, k]}, 2^d <= k < 2^(d+1)]; Select[Range[500], q] (* Amiram Eldar, May 01 2025 *)

PARI

isok(k) = my(d = numdiv(k)); 2^d <= k && k < 2^(d+1); \\ Amiram Eldar, May 01 2025