A338506 a(n) is the number of subsets of divisors of n.

2, 4, 4, 8, 4, 16, 4, 16, 8, 16, 4, 64, 4, 16, 16, 32, 4, 64, 4, 64, 16, 16, 4, 256, 8, 16, 16, 64, 4, 256, 4, 64, 16, 16, 16, 512, 4, 16, 16, 256, 4, 256, 4, 64, 64, 16, 4, 1024, 8, 64, 16, 64, 4, 256, 16, 256, 16, 16, 4, 4096, 4, 16, 64, 128, 16, 256, 4, 64

Offset: 1

Author

Rémy Sigrist, Oct 31 2020

Keywords

• nonn
• easy

Comments

In contrast to A100587, we take into account the empty set.

Examples

			For n = 6:
- 6 has 4 divisors,
- so a(n) = 2^4 = 16.
		

Links

• Rémy Sigrist, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000005, A100587.

Programs

Mathematica

Table[2^DivisorSigma[0, n], {n, 68}]

PARI

a(n) = 2^numdiv(n)

Formula

a(n) = 2^A000005(n) = A100587(n) + 1.