

A116504


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


18



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, 6, 11, 9, 6
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OFFSET

1,2


LINKS

Table of n, a(n) for n=1..93.


EXAMPLE

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


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 *)


PROG

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


CROSSREFS

Cf. A116505.
Cf. A000422, A116504, A007908, A116505, A104759, A138789, A138790, A138793.
Sequence in context: A278597 A138789 A129654 * A186233 A226056 A104011
Adjacent sequences: A116501 A116502 A116503 * A116505 A116506 A116507


KEYWORD

nonn,base


AUTHOR

Parthasarathy Nambi, Mar 20 2006


EXTENSIONS

Edited and extended by Klaus Brockhaus, Mar 29 2006
Terms a(59)a(93) from Sean A. Irvine, Nov 04 2009


STATUS

approved



