A077809 Number of divisors of numbers containing in their decimal representation only the digits 0 and 1.

1, 4, 2, 9, 2, 8, 4, 16, 8, 8, 4, 18, 4, 16, 4, 25, 4, 32, 8, 18, 16, 16, 2, 32, 8, 16, 12, 36, 4, 16, 4, 36, 4, 16, 16, 72, 8, 32, 8, 32, 8, 64, 4, 36, 16, 8, 2, 50, 8, 32, 8, 36, 4, 48, 4, 64, 4, 16, 4, 36, 4, 16, 32, 49, 4, 16, 4, 36, 4, 64, 4, 128, 4, 32, 16, 72, 4, 32, 4, 50, 4, 32, 6

Offset

1,2

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

a(n) = A000005(A007088(n)).

Example

a(6) = A000005(A007088(6)) = A000005(110) = 8, as 110 has divisors: 1, 2, 5, 10, 11, 22, 55 and 110.

Mathematica

With[{z1=Rest[FromDigits/@Tuples[{0, 1}, 7]]}, DivisorSigma[0, #]&/@z1] (* Harvey P. Dale, Sep 19 2021 *)

Prog

(PARI) a(n) = numdiv(fromdigits(binary(n), 10)) \\ David A. Corneth, Sep 19 2021

Crossrefs

Cf. A000005, A007088, A077810.

Sequence in context: A115881 A180434 A201574 * A201281 A095303 A060734

Adjacent sequences: A077806 A077807 A077808 * A077810 A077811 A077812

Keyword

nonn,easy,base

Author

Reinhard Zumkeller, Nov 16 2002

Status

approved