OFFSET
0,2
FORMULA
a(n)=Product{k=0..n, (floor(5(2k+1)/2)*floor(5(2k+2)/2))^(n-k)}=Product{k=0..n, (floor(5(2k+1)/2)*5(k+1))^(n-k)}.
a(n) ~ (2*Pi)^(n + 7/10) * 5^(n*(n+1)) * n^(n^2 + 7*n/5 + 31/75) / (A * Gamma(2/5)^(n + 2/5) * exp(3*n^2/2 + 7*n/5 - 1/12 - c)), where A is the Glaisher-Kinkelin constant A074962 and c = zeta'(-1, 2/5) = 0.0827672925828924139907562934385991589097620172389278574723... - Vaclav Kotesovec, Jan 23 2024
MATHEMATICA
Table[Product[(Floor[5*(2*k+1)/2]*5*(k+1))^(n-k), {k, 0, n}], {n, 0, 10}] (* Vaclav Kotesovec, Jan 23 2024 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Dec 03 2009
STATUS
approved