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

Author

Omar E. Pol, Apr 20 2015

Keywords

• nonn

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)

Crossrefs

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

Programs

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 *)

Formula

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