A280654 a(n) = (n!)^2 * Sum_{k=1..n} A008836(k)/k^2.

1, 3, 23, 404, 9524, 357264, 16987536, 1061800704, 87631559424, 8894837836800, 1063107188812800, 151494084266803200, 25373057708287180800, 5011895098867920076800, 1135276451701834014720000, 292340783888393707192320000, 84048723407048386326036480000

Offset

1,2

Links

Daniel Suteu, Table of n, a(n) for n = 1..100

Wikipedia, Liouville function.

Formula

Limit_{n->infinity} a(n)/(n!)^2 = zeta(4)/zeta(2) = Pi^2/15.

Mathematica

Table[(n!)^2 * Sum[(-1)^PrimeOmega[k]/k^2, {k, n}], {n, 20}] (* Indranil Ghosh, Apr 13 2017 *)

Prog

(PARI) a(n) = (n!)^2 * sum(k=1, n, (-1)^bigomega(k)/k^2);

Crossrefs

Cf. A001044, A008836, A182448 (Pi^2/15).

Sequence in context: A114601 A178315 A210910 * A118195 A055326 A271851

Adjacent sequences: A280651 A280652 A280653 * A280655 A280656 A280657

Keyword

nonn

Author

Daniel Suteu, Apr 12 2017

Status

approved