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

Offset: 0

Author

Vladeta Jovovic, Oct 03 2007

Keywords

• nonn

Links

• 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)).