OFFSET
1,3
FORMULA
Conjecture: for n>100, sum(k=1, n, a(k)) > n^(3/2)
PROG
(PARI) a(n)=sum(i=1, n, if((n^i-1)%i, 0, 1))
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Aug 21 2002
STATUS
approved