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A372872
a(n) is the total number of runs of weak ascents over all flattened Catalan words of length n.
1
1, 2, 6, 20, 67, 222, 728, 2368, 7653, 24602, 78730, 250956, 797159, 2524342, 7971612, 25110584, 78918985, 247518642, 774840974, 2421378052, 7554699531, 23535794702, 73222472416, 227512682160, 706073841197, 2188828907722, 6778308875538, 20970393083708, 64817578622383
OFFSET
1,2
LINKS
Jean-Luc Baril, Pamela E. Harris, and José L. Ramírez, Flattened Catalan Words, arXiv:2405.05357 [math.CO], 2024. See p. 10.
FORMULA
From Baril et al.: (Start)
G.f.: x*(1 - 2*x)^3/(1 - 4*x + 3*x^2)^2.
a(n) = (27 - 9*n + (5 + n)*3^n)/36. (End)
E.g.f.: (exp(3*x)*(5 + 3*x) - 9*exp(x)*(x - 3) - 32)/36.
MATHEMATICA
LinearRecurrence[{8, -22, 24, -9}, {1, 2, 6, 20}, 29]
CROSSREFS
Sequence in context: A108627 A193234 A285197 * A148475 A148476 A148477
KEYWORD
nonn,easy
AUTHOR
Stefano Spezia, May 15 2024
STATUS
approved