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 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS 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

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Last modified October 13 16:50 EDT 2019. Contains 327968 sequences. (Running on oeis4.)