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 A117738 #2 Mar 30 2012 17:31:18
%S A117738 1,1,3,23,43,13,87,71,153,11,19,13,89,219,119,459,1,129,633,131,71,
%T A117738 217,1091,911,1141,511,143,201,377,379,371,377,83,201,993,53,143,307,
%U A117738 423,919,259,263,759,3933,3,1781,607,2327,7683,541,3443,6507,4023,3399,899
%N A117738 Least number d such that 10^n -/+ 3d form a prime pair.
%F A117738 A115564(n)/3.
%t A117738 f[n_] := Block[{k = 1}, While[ ! PrimeQ[10^n - 3k] || ! PrimeQ[10^n + 3k], k++ ]; k]; Array[f, 55]
%K A117738 nonn
%O A117738 1,3
%A A117738 _Robert G. Wilson v_, Apr 12 2006