A048253 a(n) is the number of integers whose sum of divisors is 6^n.

1, 1, 1, 5, 11, 18, 30, 48, 85, 148, 250, 415, 669, 1066, 1697, 2635, 4036, 6111, 9137, 13540, 19930, 29098, 42184, 60655, 86598, 122821, 173314, 243469, 340329, 473221, 654779, 901741, 1236668, 1689322, 2298592, 3115200, 4206016, 5658677, 7588039

Offset

0,4

Links

Ray Chandler, Table of n, a(n) for n = 0..1000

Example

For n=3, sigma(1,k) = 6^3 = 216 for each of 5 integers: 102, 110, 142, 159, and 187, so a(3) = 5.

Mathematica

With[{s = Array[DivisorSigma[1, #] &, 6^8]}, Array[Count[s, 6^#] &, Log[6, Length@ s] + 1, 0]] (* Michael De Vlieger, May 14 2018 *)

Prog

(PARI) a(n) = sum(k=1, 6^n, sigma(k)==6^n); \\ Michel Marcus, May 14 2018

Crossrefs

Cf. A006532, A020477, A019422, A019423, A018427, A048251-A048256.

Sequence in context: A240438 A365417 A140697 * A102174 A140515 A056996

Adjacent sequences: A048250 A048251 A048252 * A048254 A048255 A048256

Keyword

nonn

Author

Labos Elemer

Extensions

a(9)-a(14) from Donovan Johnson, Sep 02 2008

Edited and extended by Ray Chandler, Sep 01 2010

Status

approved