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A006587 a(n) = 3*2^(2*n)*(3*n)!/((2*n)!*n!). 1
3, 36, 720, 16128, 380160, 9225216, 228114432, 5715394560, 144599482368, 3685869158400, 94513444945920, 2435255516528640, 62999001405849600, 1635260233414606848, 42568679092062781440, 1110895735754245275648 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

REFERENCES

W. A. Whitworth, DCC Exercises in Choice and Chance, Stechert, NY, 1945, p. 35.

LINKS

Table of n, a(n) for n=0..15.

M. Le Brun, Email to N. J. A. Sloane, Jul 1991

MAPLE

A006587:=n->3*2^(2*n)*(3*n)!/((2*n)!*n!); seq(A006587(n), n=0..50); # Wesley Ivan Hurt, Nov 23 2013

MATHEMATICA

Table[3*2^(2n)(3n)!/((2n)!*n!), {n, 0, 50}] (* Wesley Ivan Hurt, Nov 23 2013 *)

PROG

(PARI) a(n)=3*binomial(3*n, n)*4^n \\ Charles R Greathouse IV, Aug 11 2017

CROSSREFS

Sequence in context: A223912 A224184 A241996 * A091482 A121245 A193754

Adjacent sequences:  A006584 A006585 A006586 * A006588 A006589 A006590

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified February 22 13:09 EST 2018. Contains 299454 sequences. (Running on oeis4.)