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 A364696 #18 Oct 07 2023 07:01:26
%S A364696 0,2,77,24587,48070640,471412484,7471587112
%N A364696 Nonnegative integers k such that the sum of the first k primes is a pentagonal number.
%H A364696 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentagonal_number">Pentagonal number</a>.
%H A364696 <a href="/index/Pol#polygonal_numbers">Index to sequences related to polygonal numbers</a>
%e A364696 2 is a term because the sum of the first 2 primes (2 + 3 = 5) is a pentagonal number.
%t A364696 A364696list[kmax_]:=Module[{p=0},Join[{0},Table[If[IntegerQ[(Sqrt[24(p+=Prime[k])+1]+1)/6],k,Nothing],{k,kmax}]]];A364696list[25000] (* _Paolo Xausa_, Oct 06 2023 *)
%Y A364696 Cf. A000326, A007504, A033997, A175133, A364691, A364695, A366270.
%K A364696 nonn,hard,more
%O A364696 1,2
%A A364696 _Paolo Xausa_, Aug 03 2023
%E A364696 a(5) from _Michel Marcus_, Aug 04 2023
%E A364696 a(6)-a(7) from _Hugo Pfoertner_, Aug 04 2023