A326824 - OEIS

%I #18 Feb 23 2020 16:28:04

%S 1,1,2,4,4,12,6,24,18,32,10,124,12,60,72,240,16,336,18,440,132,140,22,

%T 2088,100,192,378,1044,28,2096,30,4320,300,320,312,9636,36,396,408,

%U 10384,40,5040,42,3500,3000,572,46,61584,294,3920,672,5544,52,23148,680

%N a(1) = 1; a(n) = Sum_{d|n, d < n} phi(n/d) * d * a(d).

%F a(1) = 1; a(n) = Sum_{k=1..n-1} gcd(n, k) * a(gcd(n, k)).

%t a[1] = 1; a[n_] := Sum[If[d < n, EulerPhi[n/d] d a[d], 0], {d, Divisors[n]}]; Table[a[n], {n, 1, 55}]

%t a[1] = 1; a[n_] := Sum[GCD[n, k] a[GCD[n, k]], {k, 1, n - 1}]; Table[a[n], {n, 1, 55}]

%Y Cf. A000010, A001710, A006579, A006874, A018804, A165552.

%K nonn

%O 1,3

%A _Ilya Gutkovskiy_, Feb 23 2020