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A272244
a(n) = Product_{k=0..n} (n^2 + k^2).
12
0, 2, 160, 21060, 4352000, 1313845000, 547573478400, 301758856490000, 212663770808320000, 186659516597629140000, 199722414913149440000000, 255947740845844788169000000, 387074162712817024892928000000, 682170272459193898736228210000000
OFFSET
0,2
FORMULA
a(n) ~ 2^(n + 1/2) * n^(2*(n+1)) / exp((4-Pi)*n/2).
MATHEMATICA
Table[Product[n^2+k^2, {k, 0, n}], {n, 0, 15}]
KEYWORD
nonn,easy
AUTHOR
Vaclav Kotesovec, Apr 23 2016
STATUS
approved