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A307466
Number of Catalan words of length n avoiding the pattern 210.
1
1, 1, 2, 5, 14, 41, 121, 355, 1032, 2974, 8509, 24210, 68595, 193753, 546041, 1536358, 4317652, 12123685, 34021810, 95431301, 267601625, 750221859, 2102913404, 5893910702, 16517729313, 46288368894, 129710571239, 363467837569, 1018468044881, 2853791650010
OFFSET
0,3
LINKS
FORMULA
a(n) = A215404(n+2) -2*A215404(n+1) - A215404(n) -2^(n-1), n>0.
G.f.: (1-5*x+7*x^2-x^3-x^4)/(1-2*x)/(1-4*x+3*x^2+x^3) .
MAPLE
(1-5*x+7*x^2-x^3-x^4)/(1-2*x)/(1-4*x+3*x^2+x^3) ;
taylor(%, x=0, 30) ;
gfun[seriestolist](%) ;
CROSSREFS
Sequence in context: A122055 A244885 A116845 * A116849 A371427 A123183
KEYWORD
nonn,easy
AUTHOR
R. J. Mathar, Apr 09 2019
STATUS
approved