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A306988
a(n) = Sum_{k=1..n} binomial(n,k)*phi(k), where phi is the Euler totient function.
7
1, 3, 8, 20, 49, 117, 272, 620, 1395, 3107, 6852, 14964, 32395, 69647, 149002, 317712, 675749, 1433769, 3033444, 6396320, 13437913, 28130869, 58708304, 122239396, 254141275, 527946013, 1096312050, 2275897660, 4722500707, 9791471587, 20277706762, 41932520528
OFFSET
1,2
LINKS
Eric Weisstein's World of Mathematics, Totient Function.
FORMULA
a(n) ~ 3 * n * 2^n / Pi^2.
MATHEMATICA
Table[Sum[Binomial[n, k]*EulerPhi[k], {k, 1, n}], {n, 1, 40}]
CROSSREFS
Partial sums of A131045.
Sequence in context: A018792 A360263 A018791 * A026723 A038746 A126876
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Mar 18 2019
STATUS
approved