A331017 Numbers that equal to the sum of their iterated absolute alternating sum-of-divisors function (A206369).

3, 10, 21, 63, 104, 152, 170, 358, 567, 651, 3826, 4664, 5583, 5943, 39248, 943228, 1906503, 9166540, 35702868, 701792828, 825415941, 2275142000, 5805372939

Offset

1,1

Links

Table of n, a(n) for n=1..23.

Example

10 is a term since the iterations of A206369 with a starting value of 10 give A206369(10) = 4, A206369(4) = 3, A206369(3) = 2, and A206369(2) = 1, whose sum is 4 + 3 + 2 + 1 = 10.

Mathematica

f[p_, e_] := Sum[(-1)^(e - k)*p^k, {k, 0, e}]; s[1] = 1; s[n_] := s[n] = Times @@ (f @@@ FactorInteger[n]); Select[Range[1000], Plus @@ FixedPointList[s, #] == 2 # + 1 &]

Crossrefs

Cf. A082897, A206369, A330786 (number of iterations).

Sequence in context: A355389 A081950 A204340 * A207646 A071563 A360632

Adjacent sequences: A331014 A331015 A331016 * A331018 A331019 A331020

Keyword

nonn,more

Author

Amiram Eldar, Jan 06 2020

Status

approved