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 A240748 #25 May 17 2014 02:52:08 %S A240748 2,4,5,6,10,13 %N A240748 Numbers n such that n^k - (n-1)^k - ... - 3^k - 2^k - 1 is prime for some k. %C A240748 a(7) > 13. See A240747 for more information. %C A240748 a(n) is also the n-values such that A240747(n) is nonzero. %C A240748 It is known that a(n) == 1 mod 4 or 2 mod 4 (except a(2) = 4). %C A240748 If n is not squarefree, then n is not a member of this sequence. %C A240748 It is known that 17, 22, 30, 41, 66, and 194 are members of this sequence. %e A240748 There are primes of the form 2^k-1 (A000043) so 2 is a member of this sequence. %o A240748 (PARI) s(n) = for(k=1,6000,if(ispseudoprime(n^k-sum(i=1,n-1,i^k)),return(k))) %o A240748 n=1; while(n<200,if(s(n),print(n));n+=1) %Y A240748 Cf. A000043, A240747, A240507, A240503. %K A240748 nonn,more,hard %O A240748 1,1 %A A240748 _Derek Orr_, Apr 11 2014