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 A271392 #23 Aug 10 2024 09:29:17 %S A271392 2,4,5,8,9,15,16,23,27,32,34,35,38,40,46,54,57,83,87,97,162,165,223, %T A271392 235,282,488,503,575,673,823,857,885,965,1112,1401,2288,2569,2788, %U A271392 3133,3539,4070,4654,5020,5613,6720,7773,11256,18023,22196 %N A271392 Integers k such that 3*k!!! + 1 is prime where k!!! is A007661(k). %C A271392 Corresponding primes are 7, 13, 31, 241, 487, 87481, 174721, 289027201, 21427701121, ... %e A271392 4 is a term because 3*4!!! + 1 = 13 is prime. %o A271392 (PARI) is(k) = ispseudoprime(3*prod(i=0, (k-2)\3, k-3*i) + 1); \\ _Jinyuan Wang_, Jun 09 2021 %Y A271392 Cf. A007661, A037083, A084438, A217647, A215779, A271396. %K A271392 nonn,more %O A271392 1,1 %A A271392 _Altug Alkan_, Apr 06 2016 %E A271392 a(47) from _Jinyuan Wang_, Jun 09 2021 %E A271392 a(48)-a(49) from _Michael S. Branicky_, Aug 10 2024