OFFSET
0,3
FORMULA
a(n) = (2*n)! * [x^(2*n)] ((log(1 + I*x/sqrt(2)) - log(1 - I*x/sqrt(2)))/2)^2.
MAPLE
ser := series(arctan(x / sqrt(2))^2, x, 38):
seq((2*n)! * coeff(ser, x, 2*n), n = 0..17);
CROSSREFS
KEYWORD
sign
AUTHOR
Peter Luschny, Sep 03 2022
STATUS
approved