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
KEYWORD
frac,nonn
AUTHOR
Artur Jasinski, Mar 03 2010
EXTENSIONS
Name simplified by Peter Luschny, Nov 14 2017
STATUS
approved