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)
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
KEYWORD
nonn
AUTHOR
Omar E. Pol, Apr 20 2015
STATUS
approved