1,2

Numbers A003415(k) / A000005(k) such that A000005(k) divides A003415(k).

Table of n, a(n) for n=1..73.

a(n) = A003415(A351048(n)) / A000005(A351048(n)). - Amiram Eldar, Feb 03 2022

a(7) = 4; A351048(7) = 39, so tau(39) = 4 | 16 = 39'. Then a(7) = 39'/tau(39) = 16/4 = 4.

r[1] = 0; r[n_] := Module[{f = FactorInteger[n]}, n * Plus @@ ((Last[#]/First[#]) & /@ f) / Times @@ (1 + Last[#] & /@ f)]; Select[Table[r[n], {n, 1, 500}], IntegerQ] (* Amiram Eldar, Feb 03 2022 *)

Cf. A000005 (tau), A003415 (arithmetic derivative), A351048.

Sequence in context: A111739 A182214 A339505 * A216161 A332502 A287870

Adjacent sequences: A351160 A351161 A351162 * A351164 A351165 A351166

nonn

Wesley Ivan Hurt, Feb 03 2022

approved