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A152296 Let f(M,N)=2^(-M)*sum_{i=0..N} {(-1)^{i}M!N!(2M-2i)!}/{i!(M-i)!(N-i)!6^{N-i}}; then a(n) = f(3n,n). 2
1, 6, 113400, 32901422400, 67651716132000000, 608762379843757339200000, 17903325789347617610786995200000, 1415199921956087613201896962521600000000, 261375521452474271183649591888039276441600000000, 101519644940256627137917269623207295713536128000000000000, 76392226231236455854222646891536244623780022885776896000000000000 (list; graph; refs; listen; history; internal format)
OFFSET

0,2

CROSSREFS

A variant of A132202. Cf. A134648, A134772, A152296.

Sequence in context: A086897 A034208 A003834 * A076909 A172864 A183765

Adjacent sequences:  A152293 A152294 A152295 * A152297 A152298 A152299

KEYWORD

nonn

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com), Oct 18 2009

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Last modified February 14 07:16 EST 2012. Contains 205589 sequences.