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

1,2

Links

Table of n, a(n) for n=1..25.

Prog

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

Crossrefs

Cf. A000010, A001088, A028415, A048049.

Sequence in context: A332791 A291484 A145997 * A109139 A038576 A002358

Adjacent sequences: A067575 A067576 A067577 * A067579 A067580 A067581

Keyword

nonn

Author

Benoit Cloitre, Jan 30 2002

Extensions

More terms from Michel Marcus, Jan 09 2021

Status

approved