A344577 - OEIS

A344577

a(n) = Sum_{d|n, d<n} phi(n-d) for n >= 2.

1, 1, 3, 2, 8, 2, 10, 6, 14, 4, 26, 4, 22, 14, 22, 8, 42, 6, 44, 20, 30, 10, 70, 16, 40, 26, 56, 12, 102, 8, 66, 34, 52, 36, 116, 12, 66, 42, 110, 16, 140, 12, 100, 68, 66, 22, 176, 28, 118, 52, 104, 24, 178, 58, 164, 60, 88, 28, 288, 16, 106, 100, 138, 72, 212, 20, 166, 74

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OFFSET

2,3

COMMENTS

If p is prime, a(p) = phi(n-1).

LINKS

Table of n, a(n) for n=2..69.

EXAMPLE

a(10) = Sum_{d|10, d<10} phi(10-d) = phi(10-1) + phi(10-2) + phi(10-5) = 6 + 4 + 4 = 14.

MATHEMATICA

Table[Sum[EulerPhi[n - k] (1 - Ceiling[n/k] + Floor[n/k]), {k, n - 1}], {n, 100}]

CROSSREFS