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 A188339 #26 Jul 23 2023 01:52:10 %S A188339 5,53,61,193,227,257,307,317,383,457,577,601,607,653,727,751,947,1019, %T A188339 1031,1039,1049,1093,1123,1193,1259,1283,1409,1471,1483,1607,1613, %U A188339 1667,1987,2011,2029,2203,2357,2371,2377,2909,2939,3011,3049,3089,3163 %N A188339 Primes p such that 2^p mod p^2 is prime. %H A188339 Felix Fröhlich, <a href="/A188339/b188339.txt">Table of n, a(n) for n = 1..3119</a> (all terms up to 10^6) %e A188339 5 is a term because 5 is prime and (2^5 mod 5^2) = 32 mod 25 = 7 also prime. %t A188339 Select[Prime[Range[500]], PrimeQ[PowerMod[2,#, #^2]] &] (* _Alonso del Arte_, Mar 28 2011 *) %o A188339 (PARI) forprime(p=2, 10^3, if(isprime(2^p%p^2), print1(p, ", "))) \\ _Felix Fröhlich_, Jun 28 2014 %Y A188339 Cf. A066606. %K A188339 nonn %O A188339 1,1 %A A188339 _Juri-Stepan Gerasimov_, Mar 28 2011