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 A247044 #7 Sep 22 2014 19:42:36 %S A247044 3,2,1,1,2,1,1,3,6,7,14,1,8,1,2,4,2,5,16,26,27,2,18,29,9,15,7,2,24,1, %T A247044 44,1,1,209,12,128,20,1,18,5,6,3,21,5,42,6,45,19,14,10,8,20,72,8,226, %U A247044 11,5,77,99,28,16,15,157,9,24,17,110,9,28,26,16,37,163,79,29,45,58,21,66 %N A247044 Least number k > 0 such that k!*n! - 1 is prime. %C A247044 If a(n) = K, a(K) <= n for all n. %C A247044 a(n) = 1 if and only if n is in A002982. %o A247044 (PARI) %o A247044 a(n)=k=1;while(!ispseudoprime(k!*n!-1),k++);k %o A247044 n=1;while(n<100,print1(a(n),", ");n++) %Y A247044 Cf. A002982, A231549. %K A247044 nonn %O A247044 1,1 %A A247044 _Derek Orr_, Sep 10 2014