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A248707 f(3n)/(f(n-1)*f(n)*f(n+1)), where f(k) = k!. 4
3, 60, 1260, 27720, 630630, 14702688, 349188840, 8413788240, 205086088350, 5046360719400, 125149745841120, 3124367780788800, 78443948210518800, 1979201154850012800, 50151543548788717200, 1275619260617425959840, 32554866547007225016750 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
These are multinomial coefficients.
LINKS
FORMULA
a(n) ~ 3^(3*n+1/2) / (2*Pi*n). - Vaclav Kotesovec, Oct 19 2014
From Robert Israel, Mar 02 2017: (Start)
G.f.: 3*x*hypergeom([4/3, 5/3], [3], 27*x).
n(n+2)a(n+1) = 3(3n+1)(3n+2)a(n).
(End)
EXAMPLE
a(2) = 6!/(1!*2!*3!) = 60.
MAPLE
seq(3*(3*n-1)!/((n-1)!^3*n*(n+1)), n=1..20); # Robert Israel, Mar 02 2017
MATHEMATICA
Table[(3 n)!/((n - 1)! n! (n + 1)!), {n, 1, 20}]
CROSSREFS
Sequence in context: A183251 A001084 A137150 * A219870 A326283 A259268
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Oct 12 2014
STATUS
approved

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Last modified May 26 08:09 EDT 2024. Contains 372807 sequences. (Running on oeis4.)