This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A349750 #12 Dec 04 2021 12:31:02 %S A349750 1,15,25,33,45,51,69,87,91,99,105,121,123,133,135,141,147,153,159,165, %T A349750 177,195,207,213,217,231,247,249,255,259,261,267,285,289,297,301,303, %U A349750 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 %N A349750 Odd numbers k such that sigma(k) == k (mod 3), where sigma is the sum of divisors function. %C A349750 Odd numbers k such that A010872(k) is equal to A074941(k). %C A349750 Odd numbers k for which A001065(k) is a multiple of 3. %H A349750 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a> %t A349750 Select[Range[1, 500, 2], Divisible[DivisorSigma[1, #] - #, 3] &] (* _Amiram Eldar_, Dec 01 2021 *) %o A349750 (PARI) isA349750(n) = ((n%2)&&0==(sigma(n)-n)%3); %Y A349750 Cf. A000203, A001065, A010872, A074941, A349749, A349751. %K A349750 nonn %O A349750 1,2 %A A349750 _Antti Karttunen_, Nov 30 2021