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 A201456 #5 Mar 30 2012 18:36:00
%S A201456 3,3,9,9,3,3,51,57,101,5,23,59,51,161,3,5,93,135,41,29,57,5,111,129,
%T A201456 113,35,11,15,107,129,167,21,11,143,261,57,137,113,203,219,53,101,263,
%U A201456 137,309,101,261,87,99,239,369,59,123,83,3,275,227,321,221,27,81,135,57,29,17,281,71,359,27,395,261,99,21,215,323,71,63,29
%N A201456 Least k such that (7^n + k)*7^n + 1 is a prime number.
%t A201456 Table[k = 0; While[!PrimeQ[(7^n + k)*7^n + 1], k++]; k, {n, 85}]
%Y A201456 Cf. A191617, A200920, A201133.
%K A201456 nonn
%O A201456 1,1
%A A201456 _Michel Lagneau_, Dec 01 2011