%I #5 May 23 2021 21:43:27

%S 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,

%T 56,12,102,8,66,34,52,36,116,12,66,42,110,16,140,12,100,68,66,22,176,

%U 28,118,52,104,24,178,58,164,60,88,28,288,16,106,100,138,72,212,20,166,74

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

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

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

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

%Y Cf. A000010 (phi).

%K nonn

%O 2,3

%A _Wesley Ivan Hurt_, May 23 2021