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A127769
a(n)=3*C(4n-2,2n)/(2n+1)-2*0^n.
3
1, 1, 9, 90, 1001, 11934, 149226, 1931540, 25662825, 347993910, 4796857230, 67016296620, 946844533674, 13505406670700, 194214400834356, 2812744285440936, 40989428837821289, 600607911737487654, 8843512890953152230, 130783058462384959036
OFFSET
0,3
COMMENTS
a(n)=A127768(2n).
LINKS
FORMULA
Conjecture: n*(2*n+1)*(2*n-3)*a(n) -2*(4*n-5)*(4*n-3)*(2*n-1)*a(n-1)=0, n>1. - R. J. Mathar, Nov 12 2014
MATHEMATICA
Join[{1}, Table[(3*Binomial[4n-2, 2n])/(2n+1), {n, 20}]] (* Harvey P. Dale, Mar 14 2012 *)
CROSSREFS
Cf. A127768.
Sequence in context: A082367 A276506 A049389 * A276961 A062815 A294610
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Jan 28 2007
STATUS
approved