A328043 Number of divisors of the amicable pairs.

12, 6, 12, 12, 12, 12, 12, 12, 16, 12, 16, 16, 32, 16, 20, 10, 24, 12, 20, 20, 32, 32, 48, 24, 32, 16, 48, 24, 48, 24, 20, 20, 24, 16, 32, 16, 20, 20, 20, 20, 32, 16, 24, 24, 36, 12, 24, 12, 48, 16, 32, 16, 20, 20, 18, 36, 20, 20, 48, 48, 32, 16, 32, 16, 32, 16, 32, 16, 32, 16, 48, 24, 32, 16, 48, 32, 24, 20

Offset: 1

Author

Omar E. Pol, Oct 02 2019

Keywords

• nonn

Examples

			Consider the first amicable pair [220, 284]. The smaller member has 12 divisors, they are 1, 2, 4, 5, 10, 11, 20, 22, 44, 55, 110, 220. The larger member has 6 divisors, they are 1, 2, 4, 71, 142, 284. So a(1) = 12 and a(2) = 6.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..20000

Crossrefs

Row lengths of A328009.

Cf. A000005, A259180, A328063, A328064, A328065.

Programs

Mathematica

With[{s = Array[{#, DivisorSigma[1, #] - #} &, 10^5]}, DivisorSigma[0, #] &@ Flatten@ DeleteDuplicates[Sort /@ Select[Reverse /@ s, And[! FreeQ[s, #], UnsameQ @@ #] &]]] (* Michael De Vlieger, Oct 08 2019 *)

Formula

a(n) = A000005(A259180(n)).