A369661 Numbers k whose arithmetic derivative k' is of the form 4m+2, and k' has an even number of prime factors.

9, 21, 25, 33, 49, 57, 69, 85, 93, 121, 129, 133, 145, 169, 177, 205, 213, 217, 237, 249, 253, 265, 289, 309, 329, 361, 375, 393, 417, 445, 459, 469, 473, 489, 493, 505, 517, 529, 533, 553, 565, 573, 581, 597, 629, 633, 669, 685, 697, 713, 753, 781, 783, 793, 813, 817, 819, 841, 865, 869, 875, 889, 913, 933, 949, 961

Offset: 1

Author

Antti Karttunen, Feb 06 2024

Keywords

• nonn

Comments

Equally, numbers k whose arithmetic derivative k' is congruent to 2 modulo 4 and A276085(k') is congruent to 3 modulo 4.

Numbers k such that A003415(k) is in A369966.

For all n >= 1, A003415((1/2)*A003415(a(n))) is odd.

Links

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

Crossrefs

Setwise difference A327862 \ A369662.

Cf. A003415, A369660 (characteristic function), A369966.

Subsequences: A108181, A369663 (terms of the form 4m+3).

Programs

PARI

\\ See A369660.