A091437 - OEIS

A091437

Number of bipartite partitions of ceiling(n/2) white objects and floor(n/2) black ones.

1, 1, 2, 4, 9, 16, 31, 57, 109, 189, 339, 589, 1043, 1752, 2998, 4987, 8406, 13715, 22652, 36535, 59521, 94664, 151958, 239241, 379693, 591271, 927622, 1431608, 2224235, 3402259, 5236586, 7947530, 12130780, 18272221, 27669593, 41393154

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OFFSET

0,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..100

MATHEMATICA

max = 35; se = Series[ Sum[ Log[1 - x^(n - k)*y^k], {n, 1, 2max}, {k, 0, n}], {x, 0, 2max}, {y, 0, 2max}]; coes = CoefficientList[ Series[ Exp[-se], {x, 0, 2max}, {y, 0, 2max}], {x, y}]; a[n_] := coes[[ Ceiling[(n+2)/2], Floor[(n+2)/2] ]]; Table[a[n], {n, 0, max} ](* Jean-François Alcover, Dec 06 2011 *)

CROSSREFS

a(n) = A054225(n, [n/2]). Cf. A002774, A005380.

Sequence in context: A034449 A082894 A302831 * A131337 A062791 A203320

Adjacent sequences: A091434 A091435 A091436 * A091438 A091439 A091440

KEYWORD

nonn

AUTHOR

Christian G. Bower, Jan 08 2004

STATUS

approved