

A181367


Number of 2compositions of n containing at least one 0 entry. A 2composition of n is a nonnegative matrix with two rows, such that each column has at least one nonzero entry and whose entries sum up to n.


1



2, 6, 22, 78, 272, 940, 3232, 11080, 37920, 129648, 443008, 1513248, 5168000, 17647552, 60258304, 205746304, 702484992, 2398480128, 8189016064, 27959235072, 95459170304, 325918735360, 1112757649408, 3799195224064
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OFFSET

1,1


COMMENTS

a(n)=A181365(n,0).


REFERENCES

G. Castiglione, A. Frosini, E. Munarini, A. Restivo and S. Rinaldi, Combinatorial aspects of Lconvex polyominoes, European Journal of Combinatorics, 28, 2007, 17241741.


LINKS

Table of n, a(n) for n=1..24.


FORMULA

G.f.=2z(1z)^3/[(12z)(14z+2z^2)].


EXAMPLE

a(2)=6 because the 2compositions of 2, written as (top row / bottom row), are (1/1), (0/2), (2/0), (1,0/0,1), (0,1/1,0), (1,1/0,0), (0,0/1,1) and only the first one does not contain a 0 entry.


MAPLE

G := 2*z*(1z)^3/((12*z)*(14*z+2*z^2)): Gser := series(G, z = 0, 30): seq(coeff(Gser, z, n), n = 1 .. 25);


CROSSREFS

Cf. A181365
Sequence in context: A262068 A148496 A217528 * A106434 A150228 A203038
Adjacent sequences: A181364 A181365 A181366 * A181368 A181369 A181370


KEYWORD

nonn


AUTHOR

Emeric Deutsch, Oct 15 2010


STATUS

approved



