A068957 Number of prime divisors of n^n - (n-1)^(n-1), counted with multiplicity.

1, 1, 1, 2, 2, 1, 4, 6, 3, 1, 3, 2, 4, 3, 2, 1, 2, 3, 4, 2, 2, 3, 3, 4, 9, 4, 2, 2, 5, 4, 6, 3, 6, 4, 4, 2, 6, 7, 6, 4, 3, 4, 8, 6, 2, 7, 4, 7, 12, 6, 4, 5, 5, 7, 9, 5, 5, 6, 2, 5, 10, 4, 6, 5, 5, 3, 9, 4, 4, 2, 3, 4, 9, 4, 6, 4, 5, 7, 9, 13, 8, 4, 2, 5, 7

Offset: 2

Author

Reinhard Zumkeller, Mar 11 2002

Keywords

• nonn

Examples

			A007781(14) = 10809131718965763 = 3 * 61^2 * 968299894201, therefore a(14) = 4.
		

Crossrefs

Cf. A001222, A007781, A068956.

Programs

Mathematica

Table[ Apply[ Plus, Transpose[ FactorInteger[n^n - (n - 1)^(n - 1)]] [[ -1]]], {n, 2, 52}]

Formula

a(n) = A001222(A007781(n)).

Extensions

Edited and extended by Robert G. Wilson v, Mar 15 2002

a(53)-a(86) from Amiram Eldar, Feb 06 2020