A306509 a(n) is the number of divisors of the sum of digits of n.

1, 2, 2, 3, 2, 4, 2, 4, 3, 1, 2, 2, 3, 2, 4, 2, 4, 3, 4, 2, 2, 3, 2, 4, 2, 4, 3, 4, 2, 2, 3, 2, 4, 2, 4, 3, 4, 2, 6, 3, 2, 4, 2, 4, 3, 4, 2, 6, 2, 2, 4, 2, 4, 3, 4, 2, 6, 2, 4, 4, 2, 4, 3, 4, 2, 6, 2, 4, 4, 2, 4, 3, 4, 2, 6, 2, 4, 4, 5, 4, 3, 4, 2, 6, 2, 4, 4, 5, 2, 3, 4, 2

Offset: 1

Author

Ctibor O. Zizka, Feb 20 2019

Keywords

• nonn
• base

Examples

			a(17) = A000005(A007953(17)) = A000005(8) = 4.
		

Crossrefs

Cf. A000005, A007953.

Programs

Mathematica

Table[DivisorSigma[0,Total[IntegerDigits[n]]],{n,120}] (* Harvey P. Dale, Aug 03 2021 *)

PARI

a(n) = numdiv(sumdigits(n)); \\ Michel Marcus, Feb 20 2019

Formula

a(n) = A000005(A007953(n)).

a(10*n) = a(n). - Rémy Sigrist, Feb 25 2019