A105068 - OEIS

A105068

Number of distinct prime divisors of 10^n - 3.

1, 1, 1, 2, 2, 2, 2, 2, 3, 2, 2, 2, 3, 2, 4, 4, 1, 4, 5, 4, 2, 2, 4, 2, 2, 3, 4, 3, 4, 3, 6, 4, 3, 2, 4, 4, 5, 3, 5, 5, 4, 5, 7, 4, 5, 4, 7, 5, 4, 4, 5, 4, 3, 2, 4, 4, 2, 5, 5, 4, 4, 3, 3, 4, 2, 3, 5, 5, 6, 5, 4, 3, 3, 5, 6, 5, 5, 4, 7, 4, 3, 5, 4, 5, 5, 2, 6

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OFFSET

1,4

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..121

FORMULA

a(n) = A001221(A173833(n)). - Amiram Eldar, Jan 25 2020

EXAMPLE

If n = 1, 2 or 3, then 10^n - 3 is prime and thus the first three terms are 1.

MATHEMATICA

Table[Length[FactorInteger[10^n - 3]], {n, 1, 50}] (* Stefan Steinerberger, Feb 21 2006 *)

CROSSREFS