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 A201457 #5 Mar 30 2012 18:36:00
%S A201457 5,11,1,11,23,29,17,31,13,37,61,11,35,149,17,151,17,17,17,13,59,17,73,
%T A201457 47,43,13,113,77,119,97,125,83,13,421,103,103,77,23,23,79,5,107,7,37,
%U A201457 59,113,11,1,169,887,137,41,113,71,277,413,97,91,227,337,97,353,233,953,5,139,77,473,73,167,275,67,49,97,365,73,223,241,115
%N A201457 Least k such that (7^n + k)*7^n - 1 is a prime number.
%t A201457 Table[k = 0; While[!PrimeQ[(7^n + k)*7^n - 1], k++]; k, {n, 85}]
%Y A201457 Cf. A191618, A200921, A201134.
%K A201457 nonn
%O A201457 1,1
%A A201457 _Michel Lagneau_, Dec 01 2011