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A172651 Number of 2*n X n 0..2 arrays with row sums 2 and column sums 4. 1
1, 19, 2385, 1093050, 1328792850, 3536978063850, 18126466426218150, 163081394186253543000, 2402820978940192425615000, 54918587341306311174536985000, 1864314763102041137068549803435000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..49

FORMULA

a(n) = 24^(-n)*n!(2n)!*Sum_{i=0..n} Sum_{j=0..n-i} (3^(n-i-j)6^j*(4i+2j)!/(i!j!(n-i-j)!(2i+j)!2^(2i+j))). - Shanzhen Gao, Feb 24 2010

PROG

(PARI) a(n) = 24^(-n)*n!*(2*n)!*sum(i=0, n, sum(j=0, n-i, (3^(n-i-j)*6^j*(4*i+2*j)!/(i!*j!*(n-i-j)!*(2*i+j)!*2^(2*i+j))))); \\ Michel Marcus, Jan 17 2018

CROSSREFS

Sequence in context: A087353 A324424 A178025 * A183739 A277000 A055415

Adjacent sequences:  A172648 A172649 A172650 * A172652 A172653 A172654

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 06 2010

STATUS

approved

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Last modified May 26 19:26 EDT 2019. Contains 323597 sequences. (Running on oeis4.)