A138789 - OEIS

A138789

a(n) = number of distinct prime divisors of A104759(n).

0, 2, 2, 2, 3, 2, 2, 3, 3, 2, 2, 4, 4, 2, 5, 4, 2, 3, 7, 4, 4, 3, 3, 2, 5, 3, 5, 2, 3, 6, 6, 3, 3, 5, 5, 7, 3, 3, 4, 3, 3, 4, 4, 5, 3, 5, 7, 3, 5, 6, 6, 5, 4, 5, 2, 6, 4, 6, 4, 4, 7, 6, 5, 5, 6, 9, 5, 5, 7, 5, 5, 5, 5, 6, 6, 4, 4, 4, 5, 8, 7, 6, 4, 5, 4, 4, 9

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OFFSET

1,2

COMMENTS

Indices where number 1 occured in this sequence see A138790

LINKS

Sean A. Irvine, Table of n, a(n) for n = 1..165

FORMULA

a(n) = A001221(A104759(n)). - Michel Marcus, Jun 30 2024

MATHEMATICA

lst = {}; Do[lst = Join[lst, IntegerDigits[n]], {n, 1, 50}]; Table[Length[FactorInteger[FromDigits[Reverse[lst[[Range[1, n]]]]]]], {n, 1, Length[lst]}] (* Robert Price, Mar 24 2015 *)

CROSSREFS

Cf. A001221, A104759, A000422, A116504, A007908, A116505.

Sequence in context: A053760 A223942 A278597 * A129654 A116504 A186233

Adjacent sequences: A138786 A138787 A138788 * A138790 A138791 A138792

KEYWORD

nonn,base

AUTHOR

Artur Jasinski, Mar 30 2008

EXTENSIONS

Entire sequence corrected by Robert Price, Mar 24 2015

More terms from Sean A. Irvine, Jul 21 2024

STATUS

approved