OFFSET
1,1
COMMENTS
A066218 is a subsequence. It lists the fixed points of the transform n -> Sum_{j|n, j<n} (sigma(j)- j).
EXAMPLE
Aliquot divisors of 15450 are 1, 2, 3, 5, 6, 10, 15, 25, 30, 50, 75, 103, 150, 206, 309, 515, 618, 1030, 1545, 2575, 3090, 5150, 7725. Their respective sigma(k)-k are 0, 1, 1, 1, 6, 8, 9, 6, 42, 43, 49, 1, 222, 106, 107, 109, 630, 842, 951, 649, 4398, 4522, 5171 and their sum is equal to 17874.
Aliquot divisors of 17874 are 1, 2, 3, 6, 9, 18, 27, 54, 331, 662, 993, 1986, 2979, 5958, 8937. Their respective sigma(k)-k are 0, 1, 1, 6, 4, 21, 13, 66, 1, 334, 335, 1998, 1337, 6990, 4343 and their sum is equal to 15450.
MAPLE
with(numtheory); P:=proc(q) local a, b, c, i, n;
for n from 1 to q do a:=sort([op(divisors(n))]); b:=0;
for i from 1 to nops(a)-1 do b:=b+sigma(a[i])-a[i]; od;
a:=sort([op(divisors(b))]); c:=0;
for i from 1 to nops(a)-1 do c:=c+sigma(a[i])-a[i]; od;
if n=c then print(n); fi; od; end: P(10^6);
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Paolo P. Lava, Mar 05 2014
EXTENSIONS
a(13)-a(15) from Michel Marcus, Mar 07 2014
STATUS
approved