OFFSET
0,2
COMMENTS
p^k divides a((p^k+1)/2) for prime p>2 and integer k>0.
LINKS
Eric Weisstein's World of Mathematics, Binomial Sums.
FORMULA
a(n) = Numerator[ Sum[ (-1)^k / Binomial[2n,k]^3, {k,0,2n} ] ].
MATHEMATICA
Table[ Numerator[ Sum[ (-1)^k / Binomial[2n, k]^3, {k, 0, 2n} ] ], {n, 0, 25} ]
CROSSREFS
KEYWORD
frac,nonn
AUTHOR
Alexander Adamchuk, May 10 2007
STATUS
approved