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

2,4

Links

Table of n, a(n) for n=2..86.

Formula

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

Example

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

Mathematica

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

Crossrefs

Cf. A001222, A007781, A068956.

Sequence in context: A273903 A346420 A080928 * A119468 A175136 A091869

Adjacent sequences: A068954 A068955 A068956 * A068958 A068959 A068960

Keyword

nonn

Author

Reinhard Zumkeller, Mar 11 2002

Extensions

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

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

Status

approved