A306988 a(n) = Sum_{k=1..n} binomial(n,k)*phi(k), where phi is the Euler totient function.
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
Keywords
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 Weisstein's World of Mathematics, Totient Function.
- Wikipedia, Euler's totient function.
Programs
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Mathematica
Table[Sum[Binomial[n, k]*EulerPhi[k], {k, 1, n}], {n, 1, 40}]
Formula
a(n) ~ 3 * n * 2^n / Pi^2.