A110348 - OEIS

A110348

a(2) = 1 by definition; otherwise a(n) = A109347(n)/n.

1, 1, 8, 45, 504, 5040, 86400, 1247400, 28828800, 544864320, 15850598400, 370507737600, 12996271411200, 362038989312000, 14867734494412800, 480878287553664000, 22629566473113600000, 833522365093017600000

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..18.

FORMULA

a(2n+1) = (n+1)(n+2)...(2n-1)(2n)(2n+2) ...(3n+1)(3n+2). a(2n) = (1/2)(n+1)(n+2)...(2n-2)(2n-1)(2n+1)(2n+2)...(3n-1)(3n).

EXAMPLE

a(3) = 2*3*4/3 = 8, a(6)= 3*4*5*7*8*9/6 = 5040.

CROSSREFS

Cf. A110347.

Sequence in context: A328885 A002686 A306047 * A336999 A296945 A328198

Adjacent sequences: A110345 A110346 A110347 * A110349 A110350 A110351

KEYWORD

easy,nonn

AUTHOR

Amarnath Murthy, Jul 21 2005

EXTENSIONS

More terms from Joshua Zucker, May 08 2006

STATUS

approved