A349750 - OEIS

A349750

Odd numbers k such that sigma(k) == k (mod 3), where sigma is the sum of divisors function.

1, 15, 25, 33, 45, 51, 69, 87, 91, 99, 105, 121, 123, 133, 135, 141, 147, 153, 159, 165, 177, 195, 207, 213, 217, 231, 247, 249, 255, 259, 261, 267, 285, 289, 297, 301, 303, 315, 321, 339, 343, 345, 357, 369, 375, 393, 403, 405, 411, 423, 427, 429, 435, 441, 447, 459, 465, 469, 477, 481, 483, 495, 501, 507, 511, 519

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OFFSET

1,2

COMMENTS

Odd numbers k such that A010872(k) is equal to A074941(k).

Odd numbers k for which A001065(k) is a multiple of 3.

LINKS

Table of n, a(n) for n=1..66.

Index entries for sequences related to sigma(n)

MATHEMATICA

Select[Range[1, 500, 2], Divisible[DivisorSigma[1, #] - #, 3] &] (* Amiram Eldar, Dec 01 2021 *)

PROG