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 A248719 #8 Dec 27 2014 11:08:47 %S A248719 0,1,2,5,6,18,43,52,106,383,417,663,849,971 %N A248719 Numbers n such that 4*nextprime(2^n)^2+1 is prime. %C A248719 This sequence provides "simplest" examples of large primes of the form x^2+1, cf. A174246. %e A248719 a(1)=0 since nextprime(2^0)=2 and 4*2^2+1 = 17 is prime. %t A248719 fQ[n_] := PrimeQ[ 4NextPrime[2^n]^2 + 1]; Select[ Range@ 3000, fQ] (* _Robert G. Wilson v_, Dec 27 2014 *) %o A248719 (PARI) for(n=0,9e9,ispseudoprime(4*nextprime(2^n)^2+1)&&print1(n",")) %Y A248719 Cf. A174246. %K A248719 nonn %O A248719 1,3 %A A248719 _M. F. Hasler_, Oct 12 2014 %E A248719 a(13) and a(14) from _Robert G. Wilson v_, Dec 27 2014