OFFSET
1,2
COMMENTS
Old definition was "Denominators of partial sums for a series for (Pi^2)/8".
See the comments and the Wolfdieter Lang link.
LINKS
Wolfdieter Lang, Rationals and limit.
FORMULA
a(n) = denominator( Pi^2/2 - Zeta(2,(2*n+1)/2) ) for n > 0; see Artur Jasinski in A120268. - Bruno Berselli, Dec 02 2013
Also equals denominator( Pi^2/8 - PolyGamma(1, n+1/2)/4 ). - Jean-François Alcover, Dec 17 2013
EXAMPLE
MATHEMATICA
a[n_] := Pi^2/8 - PolyGamma[1, n+1/2]/4 // Simplify // Denominator; Table[a[n], {n, 1, 15}] (* Jean-François Alcover, Dec 17 2013 *)
PROG
(PARI) a(n) = denominator(sum(k=1, n, 1/(2*k-1)^2)); \\ Michel Marcus, May 09 2020
CROSSREFS
KEYWORD
nonn,frac,easy
AUTHOR
Wolfdieter Lang, Apr 04 2007
EXTENSIONS
Definition replaced with Lang's formula by Bruno Berselli, Dec 02 2013
STATUS
approved