login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A256259 Sum of divisors of the minimal numbers (A007416). 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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

LINKS

Table of n, a(n) for n=1..50.

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.

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 20 12:47 EDT 2019. Contains 328257 sequences. (Running on oeis4.)