A280577 - OEIS

A280577

a(n) = eulerphi(n) + floor(n/2).

1, 2, 3, 4, 6, 5, 9, 8, 10, 9, 15, 10, 18, 13, 15, 16, 24, 15, 27, 18, 22, 21, 33, 20, 32, 25, 31, 26, 42, 23, 45, 32, 36, 33, 41, 30, 54, 37, 43, 36, 60, 33, 63, 42, 46, 45, 69, 40, 66, 45, 57, 50, 78, 45, 67, 52, 64, 57, 87, 46, 90, 61, 67, 64, 80, 53, 99, 66, 78

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..69.

FORMULA

a(n) = A000010(n) + A004526(n).

G.f.: x^2/((1 + x)*(1 - x)^2) + Sum_{k>=1} mu(k)*x^k/(1 - x^k)^2. - Ilya Gutkovskiy, Jan 05 2017

MAPLE

with(numtheory): A280577:=n->phi(n)+floor(n/2): seq(A280577(n), n=1..100); # Wesley Ivan Hurt, Jan 05 2017

MATHEMATICA

Table[EulerPhi[n] + Floor[n/2], {n, 100}] (* Wesley Ivan Hurt, Jan 05 2017 *)