A134044 - OEIS

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A134044

Number of compositions of n with parts in N which avoid the pattern 221.

1, 1, 2, 4, 8, 15, 30, 58, 113, 220, 429, 835, 1627, 3169, 6172, 12023, 23419, 45616, 88853, 173073, 337118, 656656, 1279065, 2491423, 4852911, 9452731, 18412473, 35864686, 69858930, 136074521, 265052378, 516281541, 1005637564, 1958828336

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OFFSET

0,3

LINKS

Table of n, a(n) for n=0..33.

S. Heubach and T. Mansour, Enumeration of 3-letter patterns in compositions, arXiv:math/0603285 [math.CO], 2006.

FORMULA

G.f.: 1/(1-Sum(x^j*Product(1-x^(2*i),i=j+1..inf),j=1..inf)).

CROSSREFS

Sequence in context: A077596 A091865 A065494 * A079967 A192655 A018088

Adjacent sequences: A134041 A134042 A134043 * A134045 A134046 A134047

KEYWORD

nonn

AUTHOR

Vladeta Jovovic, Oct 03 2007

STATUS

approved