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A306988 a(n) = Sum_{k=1..n} binomial(n,k)*phi(k), where phi is the Euler totient function. 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 1..3280

Vaclav Kotesovec, Plot of a(n)/(n*2^n) for n = 1..5000

Eric W. Weisstein, MathWorld: Totient Function

Wikipedia, Euler's 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

Cf. A000010, A002088, A101509, A160399, A185003.

Sequence in context: A018793 A018792 A018791 * A026723 A038746 A126876

Adjacent sequences:  A306985 A306986 A306987 * A306989 A306990 A306991

KEYWORD

nonn

AUTHOR

Vaclav Kotesovec, Mar 18 2019

STATUS

approved

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Last modified October 17 14:47 EDT 2019. Contains 328114 sequences. (Running on oeis4.)