OFFSET
0,2
FORMULA
a(n) ~ 5^(5*n*(n+1)/2 + 1/2) * n^(2*n^2 - 1) / (2 * Pi * exp(3*n^2) * phi^(sqrt(5)*(n*(n+1) + 1/6) - 1/2)), where phi = A001622 is the golden ratio.
MATHEMATICA
Table[Product[i^2 + 3*i*j + j^2, {i, 1, n}, {j, 1, n}], {n, 0, 7}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Dec 10 2023
STATUS
approved