OFFSET
1,2
MATHEMATICA
Clausen[n_] := Times @@ (Select[Divisors[n + 1], PrimeQ[# + 1] &] + 1);
a[n_] := (2 n)! PolyLog[2 n, 1] Pi^(-2 n) Clausen[2 n - 1] / 2;
Table[a[n], {n, 1, 18}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, Aug 21 2021
STATUS
approved