A364561 Odd numbers k for which A156552(k) < k.

1, 3, 5, 9, 15, 21, 25, 27, 35, 45, 49, 55, 63, 75, 77, 81, 91, 99, 105, 121, 125, 135, 143, 147, 165, 169, 175, 187, 189, 195, 221, 225, 231, 243, 245, 273, 275, 289, 297, 315, 323, 325, 343, 351, 357, 363, 375, 385, 405, 425, 429, 441, 455, 495, 507, 525, 539, 561, 567, 585, 595, 605, 625, 627, 637, 663, 665

Offset: 1

Author

Antti Karttunen, Jul 28 2023

Keywords

• nonn

Comments

Odd numbers k such that A005941(k) <= k.

Links

• Antti Karttunen, Table of n, a(n) for n = 1..13739; terms less than 2^21

Crossrefs

Odd terms in A364560.

Cf. A005940, A005941, A156552, A364545, A364564 (largest prime factor).

Cf. also A364551, A364576 (subsequences).

Programs

PARI

A156552(n) = { my(f = factor(n), p, p2 = 1, res = 0); for(i = 1, #f~, p = 1 << (primepi(f[i, 1]) - 1); res += (p * p2 * (2^(f[i, 2]) - 1)); p2 <<= f[i, 2]); res };
isA364561(n) = ((n%2)&&(A156552(n) < n));