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 A133261 #2 Mar 31 2012 10:22:04
%S A133261 3,7,13,19,23,31,37,43,47,53,61,67,73,83,89,97,103,109,113,131,139,
%T A133261 151,157,167,173,181,193,199,211,223,229,233,241,251,257,263,271,277,
%U A133261 283,293,307,313,317,337,349,353,359,367,373,383,389,401,409,421,433,443
%N A133261 Union of A134196 and A134197 : A126990 with duplicates removed.
%t A133261 << NumberTheory`NumberTheoryFunctions` a = {}; Do[AppendTo[a, PreviousPrime[Sqrt[(Prime[ x - 1])*(Prime[x + 1])]]], {x, 2, 300}]; Union[a]
%Y A133261 Cf. A134196, A134197, A126990.
%K A133261 nonn
%O A133261 1,1
%A A133261 _Artur Jasinski_, Oct 15 2007