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A147291
a(n) = Sum_{k=1..n^2-1} binomial(2k,k).
1
0, 28, 17576, 209295260, 43308802158650, 150315393336149895056, 8610524734277600186228691452, 8068213695203463278728832778415607708, 122985780058082302876789680971972469134558550878, 30386103720799858392019761983012781659021124133753353112778
OFFSET
1,2
LINKS
FORMULA
a(n) ~ 4^(n^2) / (3*sqrt(Pi)*n). - Vaclav Kotesovec, Jun 07 2019
MATHEMATICA
Table[Sum[Binomial[2*k, k], {k, 1, n^2 - 1}], {n, 1, 10}] (* Vaclav Kotesovec, Jun 07 2019 *)
PROG
(PARI) a(n) = sum(k=1, n^2-1, binomial(2*k, k)); \\ Michel Marcus, Jul 05 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Apr 25 2009
STATUS
approved