A067578 a(n) = Product_{i=1..n} phi(i) * Sum_{i=1..n} 1/phi(i) where phi is the Euler totient function A000010(n).

1, 2, 5, 12, 52, 120, 752, 3200, 19968, 84480, 863232, 3637248, 44384256, 275152896, 2254307328, 18459131904, 298743496704, 1846819160064, 33568893960192, 274421835104256, 3340027488632832, 33963860494909440, 752840786973818880, 6146715129678397440, 123926213264670720000

Offset: 1

Author

Benoit Cloitre, Jan 30 2002

Keywords

• nonn

Crossrefs

Cf. A000010, A001088, A028415, A048049.

Programs

PARI

a(n) = prod(i=1, n, eulerphi(i)) * sum(i=1, n, 1/eulerphi(i)); \\ Michel Marcus, Jan 09 2021

Extensions

More terms from Michel Marcus, Jan 09 2021