A086292 Number of divisors of 7-smooth numbers.

1, 2, 2, 3, 2, 4, 2, 4, 3, 4, 6, 4, 4, 5, 6, 6, 4, 8, 3, 4, 6, 8, 6, 4, 9, 8, 8, 6, 10, 3, 6, 8, 8, 12, 6, 7, 8, 12, 6, 10, 5, 12, 12, 12, 6, 9, 8, 12, 10, 16, 4, 12, 8, 8, 12, 15, 6, 12, 12, 10, 16, 6, 18, 8, 14, 9, 12, 16, 16, 12, 9, 20, 6, 6, 8, 18, 9, 16, 16, 18, 12, 18, 12, 14

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

a(n) = A000005(A002473(n)).

Mathematica

DivisorSigma[0, Select[Range[500], Max[Transpose[FactorInteger[#]][[1]]] <= 7 &]] (* Amiram Eldar, Jan 06 2020 after G. C. Greubel at A086288 *)

Crossrefs

Cf. A000005, A002473, A086293.

Sequence in context: A193513 A218704 A144373 * A335708 A076640 A326198

Adjacent sequences: A086289 A086290 A086291 * A086293 A086294 A086295

Keyword

nonn

Author

Reinhard Zumkeller, Jul 15 2003

Status

approved