A172695 Number of 5*n X 2*n 0..2 arrays with row sums 2 and column sums 5.

51, 79796556, 19292117692187340, 130096688857163908226867520, 10585995418849686886860491452609238400, 6309193293073551526242474424812731974830376454400

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..19

Formula

a(n) = 120^(-2n)*(2n)!(5n)!*Sum_{i=0..2n} Sum_{j=0..2n-i} (10^j*15^(2n-i-j)*(4i+2j+2n)!/(i!j!(2n-i-j)!(n+j+2i)!2^(n+j+2i))). - Shanzhen Gao, Feb 24 2010

a(n) ~ sqrt(Pi) * 5^(8*n + 1/2) * n^(10*n + 1/2) / (2^(n-1) * 3^(2*n) * exp(10*n-2)). - Vaclav Kotesovec, Oct 22 2023

Mathematica

Table[120^(-2*n)*(2*n)!(5*n)! * Sum[Sum[(10^j*15^(2*n-i-j)*(4*i+2*j+2*n)!/(i!*j!*(2*n-i-j)!*(n+j+2*i)!*2^(n+j+2*i))), {j, 0, 2*n-i}], {i, 0, 2*n}], {n, 1, 12}] (* Vaclav Kotesovec, Oct 22 2023 *)

Crossrefs

Sequence in context: A135531 A038777 A281979 * A172786 A324683 A214373

Adjacent sequences: A172692 A172693 A172694 * A172696 A172697 A172698

Keyword

nonn

Author

R. H. Hardin, Feb 06 2010

Status

approved