OFFSET
0,4
COMMENTS
The trisection equals the self-convolution of this sequence.
FORMULA
G.f.: Product_{k>=0} ((1 - x^(4*3^k))/(1 - x^(3^k)))^(2^k).
G.f. A(x) satisfies: A(x) = (1 + x + x^2 + x^3) * A(x^3)^2.
MATHEMATICA
nmax = 63; CoefficientList[Series[Product[(1 + x^(3^k) + x^(2 3^k) + x^(3^(k + 1)))^(2^k), {k, 0, Floor[Log[3, nmax]] + 1}], {x, 0, nmax}], x]
nmax = 63; A[_] = 1; Do[A[x_] = (1 + x + x^2 + x^3) A[x^3]^2 + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Jul 09 2019
STATUS
approved