A369005 Numbers k for which k' / gcd(k,k') is a multiple of four, where k' stands for the arithmetic derivative of k, A003415(k).

1, 12, 15, 28, 35, 39, 44, 51, 55, 76, 81, 87, 91, 92, 95, 111, 115, 119, 123, 124, 143, 144, 155, 159, 172, 180, 183, 187, 188, 189, 203, 215, 219, 225, 235, 236, 247, 256, 259, 267, 268, 284, 287, 291, 295, 297, 299, 303, 316, 319, 320, 323, 327, 332, 335, 336, 339, 355, 371, 391, 395, 400, 403, 407, 411, 412, 415

Offset

1,2

Comments

This is a multiplicative semigroup; if m and n are in the sequence then so is m*n. - Antti Karttunen, Jun 02 2024

Links

Antti Karttunen, Table of n, a(n) for n = 1..10000

Prog

(PARI) \\ See A369004

Crossrefs

Positions of multiples of 4 in A083345.

Setwise difference A369002 \ A373265.

Subsequence of A368995, which is a subsequence of A327864, which is a subsequence of A235992.

Cf. A369004 (characteristic function).

Cf. A373259 (subsequence).

Cf. also A369644, A369007.

Sequence in context: A350807 A124521 A345666 * A134221 A179148 A194234

Adjacent sequences: A369002 A369003 A369004 * A369006 A369007 A369008

Keyword

nonn

Author

Antti Karttunen, Jan 14 2024

Status

approved