OFFSET
1,2
COMMENTS
a(49) > 10^11. - Hiroaki Yamanouchi, Aug 24 2014
LINKS
Hiroaki Yamanouchi, Table of n, a(n) for n = 1..48
EXAMPLE
The divisors of 90 are 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90 and sigma(1) + sigma(2) + sigma(3) + sigma(5) + sigma(6) + sigma(9) + sigma(10) + sigma(15) + sigma(18) + sigma(30) + sigma(45) + sigma(90) = 1 + 3 + 4 + 6 + 12 + 13 + 18 + 24 + 39 + 72 + 78 + 234 = 504 and phi(n) = 24. Finally 504 / 24 = 21.
MAPLE
with(numtheory): P:=proc(q) local a, b, k, n;
for n from 1 to q do a:=divisors(n); b:=0;
b:=add(sigma(a[k]), k=1..nops(a)); if type(b/phi(n), integer)
then print(n); fi; od; end: P(10^10);
PROG
(PARI) isok(n) = (sumdiv(n, d, sigma(d)) % eulerphi(n)) == 0; \\ Michel Marcus, Jun 04 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Jun 04 2014
EXTENSIONS
a(37)-a(40) from Hiroaki Yamanouchi, Aug 24 2014
STATUS
approved