A055023 a(n) = n/A055032(n).

1, 2, 3, 1, 5, 2, 7, 1, 1, 2, 11, 1, 13, 2, 1, 1, 17, 2, 19, 1, 3, 2, 23, 1, 1, 2, 1, 1, 29, 2, 31, 1, 1, 2, 1, 1, 37, 2, 3, 1, 41, 2, 43, 1, 1, 2, 47, 1, 1, 2, 1, 1, 53, 2, 1, 1, 3, 2, 59, 1, 61, 2, 1, 1, 1, 2, 67, 1, 1, 2, 71, 1, 73, 2, 3, 1, 1, 2, 79, 1, 1, 2, 83, 1, 1

Offset: 1

Author

N. J. A. Sloane, Jun 11 2000

Keywords

• nonn

Comments

It is conjectured that this is n iff n is 1 or a prime.

References

• R. K. Guy, Unsolved Problems Number Theory, A17.

Links

• Indranil Ghosh, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A055030, A055031, A055032, A201560, A204187.

Programs

Mathematica

Table[n/Denominator[(Sum[m^(n - 1), {m, n - 1}] + 1)/n], {n, 10}] (* Indranil Ghosh, May 17 2017 *)

PARI

a(n) = n/denominator((sum(m=1, n - 1, m^(n - 1)) + 1)/n); \\ Indranil Ghosh, May 17 2017

Python

from sympy import Integer
def a(n): return Integer(n)/((sum(m**(n - 1) for m in range(1, n)) + 1)/Integer(n)).denominator # Indranil Ghosh, May 17 2017