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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). 0
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified May 18 19:58 EDT 2021. Contains 344002 sequences. (Running on oeis4.)