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 A144974 #6 Oct 11 2019 11:44:12
%S A144974 43,71,197,463,547,953,1471,1933,2647,2843,3697,4663,5741,8233,9283,
%T A144974 10781,11173,12391,14561,18397,20483,29303,29947,34651,37493,41203,
%U A144974 46691,50821,54251,56897,57793,65213,68111,72073,76147,84631,89041
%N A144974 Centered heptagonal prime numbers.
%H A144974 Wikipedia, <a href="https://en.wikipedia.org/wiki/Centered_heptagonal_number">Centered heptagonal prime number</a>
%t A144974 lst={};Do[p=(7*n^2-7*n+2)/2;If[PrimeQ[p],AppendTo[lst,p]],{n,6!}];lst
%K A144974 nonn
%O A144974 1,1
%A A144974 _Vladimir Joseph Stephan Orlovsky_, Sep 27 2008