A256259 Sum of divisors of the minimal numbers (A007416).

1, 3, 7, 12, 28, 31, 60, 91, 124, 168, 127, 360, 403, 546, 508, 744, 1170, 1651, 2418, 2880, 2821, 3048, 2047, 4368, 3751, 5952, 9360, 9906, 8188, 12493, 8191, 19344, 15367, 22568, 22506, 24384, 28800, 26611, 39312, 32764, 51181, 59520, 49128, 79248, 99944, 92202, 112320, 116281, 106483, 160797

Offset

1,2

Comments

Has a symmetric representation in the same way as A000203 and all its subsequences.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000 (calculated from the b-file at A007416)

Formula

a(n) = A000203(A007416(n)).

Mathematica

(* The d-th element in list minDiv[n, b] is the smallest numbers k<=n with exactly d<=b divisors, otherwise it is zero. Computation stops as soon as either inequality fails. *)
minDiv[n_, b_] :=
Module[{list = Array[0 &, b], k = 1, d},
  While[k <= n, d = DivisorSigma[0, k];
   If[d <= b && list[[d]] == 0, list[[d]] = k];
   If[d <= b, k++, k = n + 2]]; list]
a256259[n_, b_] :=
Map[DivisorSigma[1, #] &, Sort[Select[minDiv[n, b], # != 0 &]]]
a256259[100000, 300] (* computes the first 60 elements of the sequence *)
(* Hartmut F. W. Hoft, Apr 27 2015 *)

Crossrefs

Cf. A000203, A005179, A007416, A007626, A053212, A063072, A081533, A237271, A237593.

Sequence in context: A196858 A099811 A196917 * A182941 A063072 A007626

Adjacent sequences: A256256 A256257 A256258 * A256260 A256261 A256262

Keyword

nonn

Author

Omar E. Pol, Apr 20 2015

Status

approved