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 A129446 #14 Jun 08 2021 02:24:06
%S A129446 2,19,79,1861,7741,1647522841025041
%N A129446 Primes p such that p^2 is a centered triangular number; or primes in A129445.
%C A129446 The next terms are too large to include, see the b-file.
%H A129446 Alexander Adamchuk, Apr 26 2007, <a href="/A129446/b129446.txt">Table of n, a(n) for n = 1..9</a>
%t A129446 Do[ f = 3n(n-1)/2 + 1; If[ PrimeQ[ Sqrt[f] ], Print[ Sqrt[f] ] ], {n,1,150000} ]
%Y A129446 Cf. A005448 (centered triangular numbers).
%Y A129446 Cf. A129444 (numbers k such that centered triangular number A005448(k) = 3*k*(k-1)/2 + 1 is a perfect square).
%Y A129446 Cf. A129445 (numbers k > 0 such that k^2 is a centered triangular number).
%K A129446 nonn
%O A129446 1,1
%A A129446 _Alexander Adamchuk_, Apr 15 2007, Apr 26 2007