A104368 Number of distinct prime factors of A104365(n) = A104350(n) + 1.

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

Offset: 1

Author

Reinhard Zumkeller, Mar 06 2005

Keywords

• nonn

Links

• Max Alekseyev, Table of n, a(n) for n = 1..158 (terms 142..151 from Tyler Busby)
• Reinhard Zumkeller, Products of largest prime factors of numbers <= n

Crossrefs

Cf. A001221, A054988, A066856, A104350, A104359, A104360, A104365, A104366, A104367, A104369, A104370, A104371, A104372.

Programs

Mathematica

A104350[n_] := Product[FactorInteger[k][[-1, 1]], {k, 1, n}]; PrimeNu[
Table[A104350[n] + 1, {n, 2, 50}]] (* G. C. Greubel, May 10 2017 *)

Formula

a(n) = A001221(A104365(n)).

Extensions

a(51)-a(76) from Amiram Eldar, Feb 12 2020

a(77)-a(81) from Jinyuan Wang, Apr 02 2020

Terms a(82) onward from Max Alekseyev, Oct 03 2022