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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 Clark Kimberling, Table of n, a(n) for n = 1..1000 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 Cf. A001700, A248708, A248709, A248710. Sequence in context: A183251 A001084 A137150 * A219870 A326283 A259268 Adjacent sequences: A248704 A248705 A248706 * A248708 A248709 A248710 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.)