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 A188717 #22 Jan 18 2025 09:06:51 %S A188717 2,17,1297,1336337,4477457,29986577,45212177,126247697,193877777, %T A188717 406586897,562448657,916636177,1416468497,1944810001,3208542737, %U A188717 4162314257,5006411537,5972816657,12444741137,19565295377,34188010001,38167092497,47156728337,59553569297,61505984017 %N A188717 Primes p such that all prime factors of p-1 have exponent 4. %H A188717 Amiram Eldar, <a href="/A188717/b188717.txt">Table of n, a(n) for n = 1..10000</a> %e A188717 17-1 = 2^4, 1297-1 = 2^4*3^4, 1336337-1 = 2^4*17^4, 4477457-1 = 2^4*23^4, ... %t A188717 Prepend[Select[Table[Prime[n],{n,600000}],Length[Union[Last/@FactorInteger[#-1]]]==1&&Union[Last/@FactorInteger[#-1]]=={4}&], 2] %t A188717 seq[lim_] := Select[Select[Range[Floor[Surd[lim-1, 2]]], SquareFreeQ]^4 + 1, PrimeQ]; seq[10^6] (* _Amiram Eldar_, Jan 18 2025 *) %o A188717 (PARI) list(lim) = select(isprime, apply(x -> x^4 + 1, select(issquarefree, vector(sqrtnint(lim-1, 4), i, i)))); \\ _Amiram Eldar_, Jan 18 2025 %Y A188717 Cf. A089195 (exponent 2), A037896 (primes of the form k^4+1), A188764. %K A188717 nonn %O A188717 1,1 %A A188717 _Vladimir Joseph Stephan Orlovsky_, Apr 09 2011 %E A188717 a(12)-a(22) from _Donovan Johnson_, Apr 10 2011 %E A188717 a(1) = 2 inserted and a(23)-a(25) added by _Amiram Eldar_, Jan 18 2025