OFFSET
0,5
FORMULA
a(n) = A344854(n) / 2^n.
a(n) = (1/6)*(hypergeom([-n/3, (1 - n)/3, (2 - n)/3], [1, 1], -27) - 1).
MAPLE
Exp := (x, m) -> sum((x^k / k!)^m, k=0..infinity):
gf := Exp(2*x, 1)*(Exp(2*x, 3) - 1): ser := series(gf, x, 34):
seq((1/6)*2^(-n)*n!*simplify(coeff(ser, x, n)), n = 0..28);
MATHEMATICA
a[n_] := (1/6) (HypergeometricPFQ[{-n/3, (1 - n)/3, (2 - n)/3}, {1, 1}, -27] - 1);
Table[a[n], {n, 0, 28}]
PROG
(Python)
from sympy import hyperexpand, Rational
from sympy.functions import hyper
def A344559(n): return (hyperexpand(hyper((Rational(-n, 3), Rational(1-n, 3), Rational(2-n, 3)), (1, 1), -27))-1)//6 # Chai Wah Wu, Jan 04 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, Jun 01 2021
STATUS
approved