login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A105973 Number of distinct prime divisors of 88...883 (with n 8's). 1
1, 1, 1, 3, 1, 2, 2, 1, 1, 5, 2, 3, 3, 2, 1, 4, 2, 2, 3, 2, 3, 6, 3, 2, 2, 4, 3, 8, 3, 5, 3, 3, 4, 5, 4, 4, 6, 4, 2, 4, 4, 5, 4, 6, 5, 7, 4, 5, 4, 2, 1, 5, 3, 2, 5, 4, 5, 4, 4, 3, 4, 2, 4, 8, 4, 5, 2, 5, 5, 5, 1, 2, 6, 5, 4, 5, 1, 2, 7, 3, 4, 9, 6, 7, 7, 4, 4, 3, 4, 5, 6, 6, 7, 5, 4, 3, 5, 5, 2, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Amiram Eldar, Table of n, a(n) for n = 0..201

FORMULA

a(n) = A001221(A173811(n+1)). - Michel Marcus, Jan 27 2014

EXAMPLE

The number of distinct prime divisors of 83 is 1 (prime).

The number of distinct prime divisors of 883 is 1 (prime).

The number of distinct prime divisors of 8883 is 3.

MATHEMATICA

Table[PrimeNu[FromDigits[PadLeft[{3}, n, 8]]], {n, 100}] (* Harvey P. Dale, Mar 08 2015 *)

PROG

a(n) = omega((8*10^(n+1)-53)/9); \\ Michel Marcus, Jan 27 2014

CROSSREFS

Cf. A104660, A104518, A104660.

Sequence in context: A236452 A056529 A087282 * A088429 A134658 A296518

Adjacent sequences:  A105970 A105971 A105972 * A105974 A105975 A105976

KEYWORD

nonn,base

AUTHOR

Parthasarathy Nambi, Apr 28 2005

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 28 09:43 EDT 2021. Contains 346325 sequences. (Running on oeis4.)