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 A173954 #25 Sep 08 2022 08:45:51
%S A173954 1,9,441,53361,1334025,481583025,254757420225,20635351038225,
%T A173954 19830572347734225,19830572347734225,3351366726767084025,
%U A173954 6196677077792338362225,13688459664843275442155025
%N A173954 a(n) = denominator of (Zeta(2, 3/4) - Zeta(2, n-1/4)), where Zeta is the Hurwitz Zeta function.
%H A173954 G. C. Greubel, <a href="/A173954/b173954.txt">Table of n, a(n) for n = 1..300</a>
%F A173954 a(n) = denominator of (Pi^2 - 8*Catalan - Zeta(2, (4 n - 1)/4)).
%F A173954 a(n) = denominator of Sum_{k=0..(n-2)} 1/(4*k+3)^2. - _G. C. Greubel_, Aug 23 2018
%p A173954 r := n -> Zeta(0, 2, 3/4) - Zeta(0, 2, n-1/4):
%p A173954 seq(denom(simplify(r(n))), n=1..13); # _Peter Luschny_, Nov 14 2017
%t A173954 Table[Denominator[FunctionExpand[-8*Catalan + Pi^2 - Zeta[2, (4*n - 1)/4]]], {n, 1, 20}] (* _Vaclav Kotesovec_, Nov 14 2017 *)
%t A173954 Denominator[Table[8*n*Sum[(-1 + 4*k + 2*n) / ((-1 + 4*k)^2*(-1 + 4*k + 4*n)^2), {k, 0, Infinity}], {n, 1, 20}]] (* _Vaclav Kotesovec_, Nov 14 2017 *)
%t A173954 Denominator[Table[Sum[1/(4*k + 3)^2, {k, 0, n-1}], {n, 1, 20}]] (* _G. C. Greubel_, Aug 23 2018 *)
%o A173954 (PARI) for(n=1,20, print1(denominator(sum(k=0,n-2, 1/(4*k+3)^2)), ", ")) \\ _G. C. Greubel_, Aug 23 2018
%o A173954 (Magma) [1] cat [Denominator((&+[1/(4*k+3)^2: k in [0..n-2]])): n in [2..20]]; // _G. C. Greubel_, Aug 23 2018
%Y A173954 For numerators see A173953.
%Y A173954 The Catalan constant is in A006752.
%Y A173954 Cf. A006752, A120268, A173945, A173947, A173948, A173949, A173953, A173955.
%K A173954 frac,nonn
%O A173954 1,2
%A A173954 _Artur Jasinski_, Mar 03 2010
%E A173954 Name simplified by _Peter Luschny_, Nov 14 2017