OFFSET
1,2
LINKS
Eric Weisstein's World of Mathematics, Totient Function.
FORMULA
a(n) ~ n! * 6*n/Pi^2.
MATHEMATICA
Table[n! * Sum[EulerPhi[k]/k, {k, 1, n}], {n, 1, 25}]
PROG
(PARI) a(n) = n!*sum(k=1, n, eulerphi(k)/k); \\ Michel Marcus, Aug 09 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Aug 09 2022
STATUS
approved