A135679 a(n) = n if n = 1 or if n is prime. Otherwise, a(n) = 2 if n is even and a(n) = 3 if n is odd.

1, 2, 3, 2, 5, 2, 7, 2, 3, 2, 11, 2, 13, 2, 3, 2, 17, 2, 19, 2, 3, 2, 23, 2, 3, 2, 3, 2, 29, 2, 31, 2, 3, 2, 3, 2, 37, 2, 3, 2, 41, 2, 43, 2, 3, 2, 47, 2, 3, 2, 3, 2, 53, 2, 3, 2, 3, 2, 59, 2, 61, 2, 3, 2, 3, 2, 67, 2, 3, 2, 71, 2, 73

Offset: 1

Author

Mohammad K. Azarian, Dec 01 2007

Keywords

• nonn
• easy

Comments

The average value of a(n) is n/(2 log n) + O(n log log n/log^2 n). - Charles R Greathouse IV, May 29 2014

Links

• G. C. Greubel, Table of n, a(n) for n = 1..1000

Programs

Mathematica

a[n_] := If[PrimeQ[n] || n == 1, n, If[EvenQ[n], 2, 3] ]; Table[a[n], {n,1,25}] (* G. C. Greubel, Oct 26 2016 *)

PARI

a(n)=if(isprime(n)||n==1, n, if(n%2, 3, 2)) \\ Charles R Greathouse IV, May 29 2014