OFFSET
0,3
FORMULA
a(n) ~ exp(2*G*n^2/Pi) / 2^(3/4), where G is Catalan's constant A006752. - Vaclav Kotesovec, Feb 14 2021
MATHEMATICA
Table[Sqrt[Product[4*Sin[j*Pi/n]^2 + 4*Sin[(2*k - 1)*Pi/(2*n)]^2, {k, 1, n}, {j, 1, n-1}]], {n, 0, 15}] // Round (* Vaclav Kotesovec, Feb 14 2021 *)
PROG
(PARI) default(realprecision, 120);
a(n) = round(sqrt(prod(j=1, n-1, prod(k=1, n, 4*sin(j*Pi/n)^2+4*sin((2*k-1)*Pi/(2*n))^2))));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Feb 13 2021
STATUS
approved