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 A225321 #6 May 06 2013 00:48:18 %S A225321 2564954,4505138,6319754,10004666,13410068,28358686,31079126,31331314, %T A225321 37983154,40470296,43452004,58717498,66643660,67991588,77422568, %U A225321 77995658,79257766,98229376,101553298,123965218,125464136,126241688,130818598,130838170,131305474 %N A225321 Numbers b such that b^(2^n) + 3 is prime for n from 0 to 4. %C A225321 Generalized Fermat numbers of the form b^(2^n) + k with k = 3 here. %t A225321 Select[Prime@Range[3, 10^6]-3, PrimeQ[#^2 + 3] && PrimeQ[#^4 + 3] && PrimeQ[#^8 + 3] && PrimeQ[#^16 + 3] &] (* _Giovanni Resta_, May 05 2013 *) %Y A225321 Cf. A070694 %K A225321 nonn %O A225321 1,1 %A A225321 _Robin Garcia_, May 05 2013 %E A225321 Missing terms a(2) and a(5) and a(12)-a(25) from _Giovanni Resta_, May 05 2013