A351562 Odd composites k such that A342926(2*k) is a multiple of 3.

15, 33, 45, 51, 69, 87, 99, 105, 123, 135, 141, 147, 153, 159, 165, 175, 177, 195, 207, 213, 231, 249, 255, 261, 267, 285, 297, 303, 315, 321, 325, 339, 345, 357, 369, 375, 393, 405, 411, 423, 429, 435, 441, 447, 459, 465, 475, 477, 483, 495, 501, 507, 519, 531, 537, 555, 561, 573, 585, 591, 609, 615, 621, 627, 639

Offset: 1

Author

Antti Karttunen, Feb 23 2022

Keywords

• nonn

Links

• Index entries for sequences related to sigma(n)

Crossrefs

Cf. A000203, A003415, A342925, A342926, A347880.

Cf. A347874 (the intersection of this sequence and A347872).

Programs

PARI

A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
A342926(n) = (A003415(sigma(n))-n);
isA351562(n) = ((n%2)&&!isprime(n)&&!(A342926(2*n)%3));