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 A264845 #12 Feb 16 2025 08:33:27
%S A264845 61,421,1321,3061,4201,4621,5521,7561,12601,14821,15601,18061,19801,
%T A264845 28621,35401,42901,44221,52561,55501,74821,76561,81901,87421,97021,
%U A264845 109201,111301,115561,117721,131101,135721,150061,189061,217561,235621,251221,270601,273901
%N A264845 Centered 20-gonal (or icosagonal) primes.
%C A264845 Primes of the form 10*k^2 - 10*k + 1.
%H A264845 OEIS Wiki, <a href="https://oeis.org/wiki/Figurate_numbers">Figurate numbers</a>
%H A264845 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CenteredPolygonalNumber.html">Centered Polygonal Number</a>
%H A264845 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PrimeNumber.html">Prime Number</a>
%t A264845 Select[Table[10 n^2 - 10 n + 1, {n, 200}], PrimeQ] (* _Vincenzo Librandi_, Nov 27 2015 *)
%o A264845 (PARI) for(n=1, 1e3, if(isprime(k=10*n^2-10*n+1), print1(k, ", "))) \\ _Altug Alkan_, Nov 26 2015
%Y A264845 Cf. A000040, A069133.
%K A264845 nonn
%O A264845 1,1
%A A264845 _Ilya Gutkovskiy_, Nov 26 2015