OFFSET
0,6
COMMENTS
The coefficients of the polygonal polynomials are the antidiagonals of A139600.
LINKS
Index entries for linear recurrences with constant coefficients, signature (-1,5,1,-8,4).
FORMULA
a(n) = (-2)^n * Sum_{k=0..n} A139600(n, k) * (-2)^(-k).
a(n) = [x^n] x*(4*x^2 - x - 1) / ((2*x + 1)^2*(x - 1)^3).
a(n) = (4 - n)*(3*n + 2 + (-2)^(n + 1)) / 27.
a(n) = - a(n-1) + 5*a(n-2) + a(n-3) - 8*a(n-4) + 4*a(n-5) for n > 4. - Chai Wah Wu, Apr 16 2025
MAPLE
a := n -> (1/27)*(4-n)*(3*n + 2 + (-2)^(n + 1)):
seq(a(n), n = 0..32);
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Peter Luschny, Feb 21 2023
STATUS
approved