A173954 a(n) = denominator of (Zeta(2, 3/4) - Zeta(2, n-1/4)), where Zeta is the Hurwitz Zeta function.

1, 9, 441, 53361, 1334025, 481583025, 254757420225, 20635351038225, 19830572347734225, 19830572347734225, 3351366726767084025, 6196677077792338362225, 13688459664843275442155025

Offset

1,2

Links

G. C. Greubel, Table of n, a(n) for n = 1..300

Formula

a(n) = denominator of (Pi^2 - 8*Catalan - Zeta(2, (4 n - 1)/4)).

a(n) = denominator of Sum_{k=0..(n-2)} 1/(4*k+3)^2. - G. C. Greubel, Aug 23 2018

Maple

r := n -> Zeta(0, 2, 3/4) - Zeta(0, 2, n-1/4):
seq(denom(simplify(r(n))), n=1..13); # Peter Luschny, Nov 14 2017

Mathematica

Table[Denominator[FunctionExpand[-8*Catalan + Pi^2 - Zeta[2, (4*n - 1)/4]]], {n, 1, 20}] (* Vaclav Kotesovec, Nov 14 2017 *)
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 *)
Denominator[Table[Sum[1/(4*k + 3)^2, {k, 0, n-1}], {n, 1, 20}]] (* G. C. Greubel, Aug 23 2018 *)

Prog

(PARI) for(n=1, 20, print1(denominator(sum(k=0, n-2, 1/(4*k+3)^2)), ", ")) \\ G. C. Greubel, Aug 23 2018
(Magma) [1] cat [Denominator((&+[1/(4*k+3)^2: k in [0..n-2]])): n in [2..20]]; // G. C. Greubel, Aug 23 2018

Crossrefs

For numerators see A173953.

The Catalan constant is in A006752.

Cf. A006752, A120268, A173945, A173947, A173948, A173949, A173953, A173955.

Sequence in context: A273889 A167720 A287102 * A239479 A229625 A196965

Adjacent sequences: A173951 A173952 A173953 * A173955 A173956 A173957

Keyword

frac,nonn

Author

Artur Jasinski, Mar 03 2010

Extensions

Name simplified by Peter Luschny, Nov 14 2017

Status

approved