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 A260298 #38 Aug 27 2016 10:18:29 %S A260298 2,3,7,47,59,79,83,103,107,127,139,191,199,211,251,263,283,307,331, %T A260298 367,379,383,431,467,479,499,503,547,587,599,607,631,643,659,727,743, %U A260298 811,823,827,839,859,863,883,887,907,971,991,1087,1151,1163,1171,1259,1283 %N A260298 Primes p such that hyperfactorial(p-1) == 1 (mod p). %C A260298 Does this contain 2 and the entries of A129518? - _R. J. Mathar_, Aug 07 2015 %C A260298 Primes p such that (p-1)!! == -1 (mod p). - _Thomas Ordowski_, Jul 26 2016 %H A260298 Matthew Campbell and Charles R Greathouse IV, <a href="/A260298/b260298.txt">Table of n, a(n) for n = 1..10000</a> (first 2516 terms from Campbell) %F A260298 a(n) = prime(A260299(n)). %t A260298 fQ[n_] := Mod[Hyperfactorial[n - 1], n] == 1; Select[ Prime@ Range@ 210, fQ] (* _Robert G. Wilson v_, Aug 06 2015 *) %o A260298 (PARI) is(p)=prod(k=2, p-1, Mod(k, p)^k)==1 && isprime(p) \\ _Charles R Greathouse IV_, Aug 05 2015 %Y A260298 Cf. A000040, A002109, A129518, A260178, A260297, A260299. %K A260298 nonn %O A260298 1,1 %A A260298 _Matthew Campbell_, Jul 22 2015