A335708 a(n) is the number of divisors of the n-th Niven number.

1, 2, 2, 3, 2, 4, 2, 4, 3, 4, 6, 6, 6, 4, 8, 4, 8, 9, 8, 8, 6, 10, 6, 8, 12, 6, 8, 12, 10, 5, 12, 12, 9, 8, 12, 8, 4, 10, 8, 6, 16, 12, 12, 4, 8, 12, 15, 12, 8, 6, 12, 10, 6, 18, 8, 14, 8, 12, 12, 4, 12, 6, 4, 16, 16, 12, 8, 12, 9, 12, 8, 12, 20, 6, 4, 18, 6, 16

Offset: 1

Author

Marius A. Burtea, Aug 04 2020

Keywords

• nonn
• base

Examples

			The first Niven number is 1 and tau(1) = 1, so a(1) = 1.
The second Niven number is 2 and tau(2) = 2, so a(2) = 2.
The 11th Niven number is 12 and tau(12) = 6, so a(11) = 6.
		

Crossrefs

Cf. A000005, A005349, A007953.

Programs

Magma

niven:=func;[#Divisors(k):k in [1..300]|niven(k)];

Mathematica

DivisorSigma[0, Select[Range[265], Divisible[#, Plus @@ IntegerDigits[#]] &]] (* Amiram Eldar, Aug 04 2020 *)

Formula

a(n) = A000005(A005349(n)).