OFFSET
1,4
COMMENTS
It is conjectured that this is 1 iff n is 1 or a prime.
REFERENCES
R. K. Guy, Unsolved Problems in Number Theory, A17.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
MAPLE
a:= proc(n) local S, m;
S:= 1;
for m from 1 to n-1 do
S:= S + m &^(n-1) mod n;
od:
denom(S/n);
end proc;
seq(a(n), n=1..1000); # Robert Israel, May 30 2014
MATHEMATICA
Table[Denominator[(Sum[m^(n - 1), {m, 1, n - 1}] + 1)/n], {n, 1, 10}] (* G. C. Greubel, Jun 06 2016 *)
PROG
(PARI) a(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 ((sum(m**(n - 1) for m in range(1, n)) + 1)/Integer(n)).denominator() # Indranil Ghosh, May 17 2017
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
N. J. A. Sloane, Jun 11 2000
STATUS
approved