OFFSET
0,3
FORMULA
a(n) ~ -2*(n-1)! * cos(n*arctan(1/(1 - sqrt(2)*3^(1/4)))) / (1 + 1/sqrt(3) - sqrt(2)/3^(1/4))^(n/2).
MATHEMATICA
nmax = 25; CoefficientList[Series[Log[1 + (1/(1 - x)^4 - 1)/4], {x, 0, nmax}], x] * Range[0, nmax]!
CROSSREFS
KEYWORD
sign
AUTHOR
Vaclav Kotesovec, May 12 2021
STATUS
approved