A116504 Number of distinct prime divisors of the concatenation of n,...,1.

0, 2, 2, 2, 3, 2, 2, 3, 3, 3, 2, 3, 3, 4, 5, 4, 6, 8, 4, 5, 4, 5, 4, 5, 6, 7, 5, 5, 7, 8, 3, 6, 5, 7, 8, 6, 4, 3, 6, 5, 8, 6, 3, 7, 6, 5, 7, 7, 3, 6, 3, 7, 9, 9, 3, 4, 4, 6, 3, 3, 5, 8, 5, 6, 7, 7, 4, 8, 8, 4, 8, 4, 7, 8, 10, 3, 7, 6, 4, 7, 7, 1, 3, 8, 3, 8, 5, 4, 5, 7, 11, 9, 6

Offset: 1

Author

Parthasarathy Nambi, Mar 20 2006

Keywords

• nonn
• base

Examples

			87654321 = 3*3*1997*4877, distinct prime divisors are 3, 1997 and 4877, hence a(8) = 3.
		

Links

• Sean A. Irvine, Table of n, a(n) for n = 1..106

Crossrefs

Cf. A116505.

Cf. A000422, A116504, A007908, A116505, A104759, A138789, A138790, A138793.

Programs

Mathematica

b = {}; a = {}; Do[w = RealDigits[n]; w = First[w]; Do[PrependTo[a, w[[Length[w] - k + 1]]], {k, 1, Length[w]}]; p = FromDigits[a]; m = FactorInteger[p]; AppendTo[b, Length[m]], {n, 1, 30}]; b (* Artur Jasinski, Mar 30 2008 *)
Table[PrimeNu[FromDigits[Flatten[IntegerDigits/@Range[n,1,-1]]]],{n,95}] (* Harvey P. Dale, Oct 03 2015 *)

PARI

{a="";for(n=1,58,a=concat(n,a);print1(omega(eval(a)),","))}

Extensions

Edited and extended by Klaus Brockhaus, Mar 29 2006

Terms a(59)-a(93) from Sean A. Irvine, Nov 04 2009

a(90) corrected by Sean A. Irvine, Nov 02 2024