

A118425


Number of binary sequences of length n containing exactly one subsequence 001.


2



0, 0, 0, 1, 4, 12, 30, 68, 144, 291, 568, 1080, 2012, 3688, 6672, 11941, 21180, 37284, 65210, 113420, 196320, 338375, 581040, 994416, 1696824, 2887632, 4902240, 8304073, 14038324, 23688636, 39905238, 67118420, 112726512, 189072363
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OFFSET

0,5


COMMENTS

With an additional 0 at the beginning, the convolution of A000071 with itself. Column 1 of A118424.


LINKS



FORMULA

G.f.=z^3/(12z+z^3)^2.


EXAMPLE

a(4)=4 because we have 0010, 0011, 0001 and 1001.


MAPLE

g:=z^3/(12*z+z^3)^2: gser:=series(g, z=0, 40): seq(coeff(gser, z, n), n=0..38);


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



