OFFSET
0,2
FORMULA
a(n) ~ c * n^(2*n^2 - 1/2) * 3^(n*(n+1)) * 2^(-n/2) * exp(n*(n+1)*(Pi - arctan(sqrt(2))) / sqrt(2) - 3*n^2) , where c = 0.4690673220228472212446336926899602910226601891141458824921925169726804439...
MATHEMATICA
Table[Product[i^2+2*j^2, {i, 1, n}, {j, 1, n}], {n, 0, 8}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Dec 05 2023
STATUS
approved