OFFSET
1,1
COMMENTS
LINKS
Paolo P. Lava, Table of n, a(n) for n = 1..1000
EXAMPLE
There is no unrelated number to 4. Therefore 0 / sigma(4) = 0 / 7 = 0 is integer.
Unrelated numbers to 10 are 4, 6, 8 and their sum is 18. Now, 18 / sigma(10) = 18 / 18 = 1, that is integer.
MAPLE
with(numtheory); P:=proc(q) local n;
for n from 1 to q do if not isprime(n) then
if type((1+n*(n+1)/2-sigma(n)-n*phi(n)/2)/sigma(n), integer)
then print(n); fi; fi; od; end: P(10^5);
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Nov 21 2014
STATUS
approved