OFFSET
0,1
LINKS
Paolo P. Lava, Table of n, a(n) for n = 0..1000
EXAMPLE
a(3) = 615: sigma(615) = sigma(390) = 615 + 390 + 3 = 1008;
a(4) = 110: sigma(110) = sigma(102) = 110 + 102 + 4 = 216;
a(5) = 435: sigma(435) = sigma(280) = 435 + 280 + 5 = 720.
MAPLE
with(numtheory): P:=proc(q) local a, b, k, n; for n from 0 to q do for k from 1 to q do
a:=sigma(k)-k-n; b:=sigma(a)-a-n; if a>0 and b=k and a<>b then print(a); break;
fi; od; od; end: P(10^9);
MATHEMATICA
Table[m = 1; While[MissingQ@ Set[k, SelectFirst[Range[m - 1], DivisorSigma[1, m] == DivisorSigma[1, #] == m + # + n &]], m++]; {k, m}, {n, 0, 10}][[All, -1]] (* Version 10.2, or *)
Do[m = 1; While[Set[k, Module[{k = 1}, While[! Xor[DivisorSigma[1, m] == DivisorSigma[1, k] == m + k + n, k >= m], k++]; k]] >= m, m++]; Print@ m, {n, 0, 10}] (* Michael De Vlieger, Apr 28 2017 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paolo P. Lava, Apr 28 2017
STATUS
approved