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

1,1

Comments

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

Links

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

Formula

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

Example

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

Mathematica

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

Prog

(PARI) a(n) = 2^numdiv(n)

Crossrefs

Cf. A000005, A100587.

Sequence in context: A140434 A308605 A107748 * A353190 A005884 A229913

Adjacent sequences: A338503 A338504 A338505 * A338507 A338508 A338509

Keyword

nonn,easy

Author

Rémy Sigrist, Oct 31 2020

Status

approved