The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A365792 a(n) = number of k <= b(n) such that rad(k) | b(n), where rad(n) = A007947(n) and b(n) = A286708(n). 3
14, 18, 15, 21, 23, 16, 19, 26, 13, 29, 30, 20, 23, 32, 14, 18, 24, 35, 36, 18, 19, 24, 28, 39, 83, 21, 40, 29, 15, 20, 42, 21, 13, 43, 18, 22, 27, 21, 15, 28, 33, 46, 91, 104, 25, 47, 34, 23, 22, 50, 24, 36, 51, 16, 120, 26, 32, 24, 52, 13, 22, 33, 39, 16, 19 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Alternatively, position of A286708(n) in the list R(rad(n)) of k such that rad(k) | n, where rad(n) = A007947(n).
LINKS
EXAMPLE
a(1) = 14 since rad(b(1)) = rad(36) = 6, and in the sequence R(6) = A003586 = {1, 2, 3, 4, 6, 8, 9, ..., 36, ...}, 36 is the 14th term.
a(2) = 18 since rad(b(2)) = rad(72) = 6, and 72 is the 18th term in R(6).
a(3) = 15 since rad(b(3)) = rad(100) = 10, and in the sequence R(10) = A003592 = {1, 2, 4, 5, 8, 10, ..., 100, ...}, 100 is the 15th term, etc.
MATHEMATICA
nn = 3300; f[x_] := f[x] = Times @@ FactorInteger[x][[All, 1]];
t = Select[
Select[Range[nn], Nor[PrimePowerQ[#], SquareFreeQ[#]] &],
AllTrue[FactorInteger[#][[All, -1]], # > 1 &] &];
s = Map[f, t];
Map[Function[k, Set[r[k], Select[Range[nn], Divisible[k, f[#]] &]]], Union@ s];
Array[FirstPosition[r[s[[#]]], t[[#]]][[1]] &, Length[t]]
CROSSREFS
Sequence in context: A154146 A113735 A063828 * A060504 A052026 A317743
KEYWORD
nonn
AUTHOR
Michael De Vlieger, Sep 22 2023
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 20 11:55 EDT 2024. Contains 372712 sequences. (Running on oeis4.)