OFFSET
0,5
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..100
FORMULA
Constant term in the expansion of Product_{k=1..2*n} (x^(2*k-1)^2+1/x^(2*k-1)^2).
EXAMPLE
For n=4 the 2 solutions are +1^2-3^2-5^2+7^2-9^2+11^2+13^2-15^2 = 0 and -1^2+3^2+5^2-7^2+9^2-11^2-13^2+15^2 = 0.
PROG
(PARI) a(n) = polcoeff(prod(k=1, 2*n, x^(2*k-1)^2+1/x^(2*k-1)^2), 0); \\ Michel Marcus, Sep 18 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Sep 17 2017
STATUS
approved