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 A264825 #11 Feb 16 2025 08:33:27 %S A264825 19,109,181,271,379,811,991,2161,3079,4159,4969,5851,7309,8929,10099, %T A264825 10711,13339,17029,21169,22051,23869,25759,26731,28729,32941,34039, %U A264825 37441,38611,39799,48619,58321,59779,67339,70489,72091,89101,90901,102079,109891,117991,122149 %N A264825 Centered 18-gonal (or octadecagonal) primes. %C A264825 Primes of the form 9*k^2 - 9*k + 1. %H A264825 OEIS Wiki, <a href="https://oeis.org/wiki/Figurate_numbers">Figurate numbers</a> %H A264825 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CenteredPolygonalNumber.html">Centered Polygonal Number</a> %H A264825 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PrimeNumber.html">Prime Number</a> %o A264825 (PARI) for(n=1, 1e3, if(isprime(k=9*n^2-9*n+1), print1(k,", "))) \\ _Altug Alkan_, Nov 26 2015 %Y A264825 Cf. A069131, A000040. %K A264825 nonn %O A264825 1,1 %A A264825 _Ilya Gutkovskiy_, Nov 26 2015