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 A267895 #20 Dec 03 2020 06:58:14 %S A267895 3,5,6,7,9,10,11,12,13,14,17,18,19,20,22,23,24,25,26,28,29,31,34,36, %T A267895 37,38,40,41,43,44,46,47,48,49,50,52,53,56,58,59,61,62,67,68,71,72,73, %U A267895 74,76,79,80,81,82,83,86,88,89,92,94,96,97,98,100,101,103,104,106,107,109 %N A267895 Numbers whose number of odd divisors is prime. %C A267895 All odd primes are in the sequence. %H A267895 Amiram Eldar, <a href="/A267895/b267895.txt">Table of n, a(n) for n = 1..10000</a> %e A267895 The divisors of 36 are 1, 2, 3, 4, 6, 9, 12, 18, 36. The odd divisors of 36 are 1, 3, 9. There are 3 odd divisors of 36 and 3 is prime, so 36 is in the sequence. %t A267895 Select[Range[100], PrimeQ[DivisorSigma[0, #/2^IntegerExponent[#, 2]]] &] (* _Amiram Eldar_, Dec 03 2020 *) %o A267895 (PARI) isok(n) = isprime(sumdiv(n, d, (d%2))); \\ _Michel Marcus_, Apr 04 2016 %Y A267895 Complement of A267894. %Y A267895 Cf. A000040, A001227, A028982, A028983, A038550, A065091, A072502, A266531, A267696, A267697. %K A267895 nonn %O A267895 1,1 %A A267895 _Omar E. Pol_, Apr 04 2016