|
|
A105248
|
|
Number of distinct prime divisors of 88...887 (with n 8's).
|
|
1
|
|
|
1, 2, 1, 1, 2, 1, 3, 3, 1, 2, 3, 1, 3, 4, 4, 4, 4, 2, 3, 3, 4, 3, 2, 3, 2, 2, 3, 5, 5, 4, 3, 4, 2, 5, 6, 2, 5, 3, 2, 3, 3, 3, 3, 3, 4, 2, 4, 2, 5, 2, 3, 5, 3, 6, 4, 5, 2, 5, 4, 3, 3, 3, 4, 2, 5, 4, 4, 5, 5, 4, 5, 1, 3, 6, 4, 2, 2, 4, 3, 4, 5, 7, 6, 5, 4, 8, 4
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,2
|
|
LINKS
|
Amiram Eldar, Table of n, a(n) for n = 0..199
|
|
FORMULA
|
a(n) = A001221(A173812(n+1)). - Michel Marcus, Jan 27 2014
|
|
EXAMPLE
|
The number of distinct prime divisors of 87 is 2.
The number of distinct prime divisors of 887 is 1 (prime).
The number of distinct prime divisors of 8887 is 1 (prime).
|
|
MATHEMATICA
|
Table[PrimeNu[(8*10^(n + 1) - 17)/9], {n, 1, 50}] (* G. C. Greubel, May 21 2017 *)
|
|
PROG
|
a(n) = omega((8*10^(n+1)-17)/9); \\ Michel Marcus, Jan 27 2014
|
|
CROSSREFS
|
Cf. A104524, A104889.
Sequence in context: A236480 A236508 A239000 * A289495 A076302 A104524
Adjacent sequences: A105245 A105246 A105247 * A105249 A105250 A105251
|
|
KEYWORD
|
nonn,base
|
|
AUTHOR
|
Parthasarathy Nambi, Apr 29 2005
|
|
EXTENSIONS
|
More terms from Brian Lauer (bel136(AT)psu.edu), Feb 23 2006
Corrected and extended by Michel Marcus, Jan 27 2014
More terms from Amiram Eldar, Jan 27 2020
|
|
STATUS
|
approved
|
|
|
|