OFFSET
1,2
FORMULA
a(n) = (n!)^n * Product_{k=1..n} (1 + (1 - 1/k)^n).
a(n) ~ n!^n * d^n, where d = exp(Integral_{x=0..1} log(1 + exp(-1/x)) dx) = 1.14183186235785012136459060138978468902610644657603999829892450823456733...
a(n) ~ (2*Pi)^(n/2) * d^n * n^(n*(2*n+1)/2) / exp(n^2 - 1/12).
MATHEMATICA
Table[Product[k^n + (k-1)^n, {k, 1, n}], {n, 1, 10}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Oct 06 2023
STATUS
approved