OFFSET
1,1
COMMENTS
For a definition of unrelated number see A045763.
EXAMPLE
There is no unrelated number to 4. Therefore 0 / (sigma(4)-4) = 0 / (7-4) = 0 is integer.
Unrelated numbers to 14 are 4, 6, 8, 10, 12 and their sum is 40. Now, 40 / (sigma(14) - 14) = 40 / (24 - 14) = 40 / 10 = 4, 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)-n), integer)
then print(n); fi; fi; od; end: P(10^5);
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Nov 21 2014
STATUS
approved