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A366575

Number of divisors of 3^n - 1.

9

2, 4, 4, 10, 6, 16, 4, 24, 8, 24, 8, 80, 4, 16, 24, 112, 8, 128, 8, 180, 16, 64, 8, 384, 24, 16, 64, 160, 16, 768, 16, 256, 32, 128, 48, 1280, 8, 64, 96, 864, 16, 768, 8, 640, 384, 32, 32, 14336, 128, 384, 64, 160, 16, 4096, 128, 1536, 128, 256, 8, 23040, 8

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OFFSET

1,1

LINKS

Max Alekseyev, Table of n, a(n) for n = 1..702

FORMULA

a(n) = sigma0(3^n-1) = A000005(A024023).

EXAMPLE

a(4)=10 because 3^4-1 has divisors {1, 2, 4, 5, 8, 10, 16, 20, 40, 80}.

MAPLE

a:=n->numtheory[tau](3^n-1):

seq(a(n), n=1..100);

MATHEMATICA

DivisorSigma[0, 3^Range[100]-1] (* Paolo Xausa, Oct 15 2023 *)

CROSSREFS

Cf. A024023, A000005, A046801, A133801, A295500, A366576.

Cf. A046801, A366602, A366612, A366621, A366633, A366652, A366661, A070528, A366683, A366709.

Sequence in context: A300549 A038043 A126138 * A363641 A247570 A054764

Adjacent sequences: A366572 A366573 A366574 * A366576 A366577 A366578

KEYWORD

nonn

AUTHOR

Sean A. Irvine, Oct 13 2023

STATUS

approved