A333263 Numbers k such that the sum of iterations of the alternating sum of divisors function A071324 starting from k is equal to 2*k.
5, 447, 700, 3122, 20649, 25816, 70221, 205701, 408624, 2574176, 3827656, 4753563, 12129928, 118200807
Offset: 1
Examples
5 is a term since the iterations of A071324 with a starting value of 5 give A071324(5) = 4, A071324(4) = 3, A071324(3) = 2, and A071324(2) = 1, whose sum is 4 + 3 + 2 + 1 = 10 = 2 * 5.
Programs
-
Mathematica
f[n_] := Plus @@ (-(d = Divisors[n])*(-1)^(Range[Length[d],1,-1])); seqQ[n_]:=Plus @@ FixedPointList[f,n] == 3n + 1; Select[Range[10000], seqQ]