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 A127042 #11 Mar 25 2020 06:51:00
%S A127042 2,3,5,7,17,19,29,31,37,41,97,127,131,211,223,227,229,233,239,241,439,
%T A127042 443,449,457,461,463,727,733,739,743,751,757,761,769,773,863,877,881,
%U A127042 883,887,967,971,977,983,991,997,1009,1013,1187,1193,1201,1901,1907,1913,1931,1933
%N A127042 Primes p such that denominator of Sum_{k=1..p-1} 1/k^2 is a square.
%H A127042 Amiram Eldar, <a href="/A127042/b127042.txt">Table of n, a(n) for n = 1..10000</a>
%t A127042 a = {}; Do[If[Sqrt[Denominator[Sum[1/x^2, {x, 1, Prime[x] - 1}]]] == Floor[Sqrt[Denominator[Sum[1/x^2, {x, 1, Prime[x] - 1}]]]], AppendTo[a, Prime[x]]], {x, 1, 50}]; a
%Y A127042 Cf. A061002, A034602, A127029.
%K A127042 nonn
%O A127042 1,1
%A A127042 _Artur Jasinski_, Jan 03 2007
%E A127042 More terms from _Franklin T. Adams-Watters_, Jan 21 2012