OFFSET
1,1
EXAMPLE
Abundant aliquot parts of 288 are 12, 18, 24, 36, 48, 72, 96, 144 and their sum is 450.
Abundant aliquot parts of 450 are 18, 30, 90, 150 and their sum is 288.
MAPLE
with(numtheory): P:=proc(q) local a, b, c, d, k, n; for n from 1 to q do
a:=sort([op(divisors(n))]); b:=0; for k from 1 to nops(a)-1 do if 2*a[k]<sigma(a[k]) then b:=b+a[k]; fi; od;
c:=sort([op(divisors(b))]); d:=0; for k from 1 to nops(c)-1 do if 2*c[k]<sigma(c[k]) then d:=d+c[k]; fi; od; if d=n and d<>b then print(n); fi; od; end: P(10^6);
MATHEMATICA
abQ[n_] := DivisorSigma[1, n] > 2n; s[n_] := DivisorSum[n, #&, #<n && abQ[#]&]; seq={}; Do[m=s[n]; If[m>n && s[m]==n, AppendTo[seq, {n, m}]], {n, 1, 10^5}]; Flatten[seq] (* Amiram Eldar, Jan 26 2019 *)
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
Paolo P. Lava, Jan 04 2017
EXTENSIONS
Data corrected and extended by Amiram Eldar, Jan 26 2019
STATUS
approved