OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..5000 (terms 1..100 from Paolo P. Lava)
EXAMPLE
(-1)sigma(1) = 1, sigma(1) = 1 and 1 / 1 = 1;
(-1)sigma(2) = 1, sigma(2) = 3 and 3 / 1 = 3;
(-1)sigma(35) = 24, sigma(35) = 48 and 48 / 24 = 2; etc.
MAPLE
with(numtheory): P:=proc(q) local a, b, i, j, n; for n from 1 to q do a:=ifactors(n)[2]:
b:=1; for i from 1 to nops(a) do b:=b*(-1+sum(a[i][1]^j, j=1..a[i][2])): od:
if type(sigma(n)/b, integer) then print(n); fi; od; end: P(10^6);
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, May 19 2015
STATUS
approved