OFFSET
0,2
LINKS
Jean-Luc Baril, Sergey Kirgizov, José L. Ramírez, and Diego Villamizar, The Combinatorics of Motzkin Polyominoes, arXiv:2401.06228 [math.CO], 2024. See Corollary 4.4 and Corollary 4.5 at pages 9-10.
FORMULA
MAPLE
gf := ((x^2+1)/sqrt((1-3*x)*(x+1))-(x+1))/(2*x): ser := series(gf, x, 40):
seq(coeff(ser, x, k), k = 0..29); # Peter Luschny, Jan 21 2024
MATHEMATICA
a[n_]:=SeriesCoefficient[(1+x^2-(1+x)Sqrt[1-2x-3x^2])/(2x*Sqrt[1-2x-3x^2]), {x, 0, n}]; Array[a, 30, 0]
CROSSREFS
KEYWORD
nonn
AUTHOR
Stefano Spezia, Jan 21 2024
STATUS
approved