OFFSET
1,2
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..100
FORMULA
a(n) ~ sqrt(Pi) * (8 - sqrt(2)*Pi - 2^(3/2) * log(1 + sqrt(2))) * 2^(2*n - 1/2) * n^(n + 3/4) / (Gamma(1/4) * exp(n)). - Vaclav Kotesovec, Jan 02 2020
MATHEMATICA
Table[Product[4*k - 3, {k, 1, n+1}] * Sum[(-1)^k/(4*k - 3), {k, 2, n+1}], {n, 1, 20}] (* Vaclav Kotesovec, Jan 02 2020 *)
PROG
(PARI) a(n)={my(s=vector(n+1, k, 4*k-3)); vecprod(s)*sum(k=2, #s, (-1)^k/s[k])} \\ Andrew Howroyd, Jan 01 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Extra initial term removed and a(11) and beyond added by Andrew Howroyd, Jan 01 2020
STATUS
approved