OFFSET
1,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..10000
FORMULA
Conjecture: (1/n)*Sum_{k=1..n} a(k) = C*log(log(n)) + o(log(log(n))) with 1 < C < 3/2.
EXAMPLE
a(5) = 3 because among the numbers 1^3+1 = 2, 2^3+1 = 9, 3^3+1 = 28, 4^3+1 = 65, and 5^3 + 1 = 126, only 3 of them (2, 9, 126) divide 5^3+1 = 126. - Petros Hadjicostas, Sep 18 2019
MAPLE
a:= n-> add(`if`(irem(n^3+1, k^3+1)=0, 1, 0), k=1..n):
seq(a(n), n=1..120); # Alois P. Heinz, Sep 18 2019
PROG
(PARI) for(n=1, 150, print1(sum(i=1, n, if((n^3+1)%(i^3+1), 0, 1)), ", "))
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, May 05 2002
STATUS
approved