OFFSET
0,2
FORMULA
a(n) ~ exp(2*G*(2*n+1)^2/Pi) / 2^(4*n + 3/4), where G is Catalan's constant A006752. - Vaclav Kotesovec, Jan 04 2021
MATHEMATICA
Table[2^(4*n^2) * Product[Product[1 - Sin[j*Pi/(2*n + 1)]^2 * Sin[k*Pi/(2*n + 1)]^2, {k, 1, n}], {j, 1, n}], {n, 0, 10}] // Round (* Vaclav Kotesovec, Jan 04 2021 *)
PROG
(PARI) default(realprecision, 120);
{a(n) = round(4^(2*n^2)*prod(j=1, n, prod(k=1, n, 1-(sin(j*Pi/(2*n+1))*sin(k*Pi/(2*n+1)))^2)))}
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jan 03 2021
STATUS
approved