OFFSET
0,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..403
FORMULA
EXAMPLE
a(1) = 3 * (1/3) = 1.
a(2) = 3*5 * (1/3 + 1/5) = 8.
a(3) = 3*5*7 * (1/3 +1/5 + 1/7) = 71.
MATHEMATICA
a[n_] := (2*n + 1)!! * Sum[1/(2*k + 1), {k, 1, n}]; Array[a, 21, 0] (* Amiram Eldar, Apr 29 2021 *)
PROG
(PARI) {a(n) = prod(k=1, n, 2*k+1)*sum(k=1, n, 1/(2*k+1))}
(PARI) {a(n) = if(n<2, n, 4*n*a(n-1)-(2*n-1)^2*a(n-2))}
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Sep 10 2020
STATUS
approved