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A349750
Odd numbers k such that sigma(k) == k (mod 3), where sigma is the sum of divisors function.
3
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
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.
MATHEMATICA
Select[Range[1, 500, 2], Divisible[DivisorSigma[1, #] - #, 3] &] (* Amiram Eldar, Dec 01 2021 *)
PROG
(PARI) isA349750(n) = ((n%2)&&0==(sigma(n)-n)%3);
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Nov 30 2021
STATUS
approved