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A140485
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Trajectory of 1 under repeated application of the map: n -> n + second-smallest number that does not divide n.
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11
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1, 4, 9, 13, 16, 21, 25, 28, 33, 37, 40, 46, 50, 54, 59, 62, 66, 71, 74, 78, 83, 86, 90, 97, 100, 106, 110, 114, 119, 122, 126, 131, 134, 138, 143, 146, 150, 157, 160, 166, 170, 174, 179, 182, 186, 191, 194, 198, 203, 206, 210, 218, 222, 227, 230, 234, 239, 242, 246
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| The numbers that do not divide 4 are 3, 5, 6, 7, ..., so a(3) = 4+5 = 9.
Here are the beginnings of the trajectories of some small numbers:
...1--4--9---13--16--21--25--28--32--37--40---
.............|...................|...|
......5--8---+...............29--+...|
.....................................|
...2--6--11--14--18--23--26--30------+
.............|...........|...........|
...3--7--10--+...........|.......33--+
.........................|
.............12--19--22--+
.................|.......|
.............15--+.......|
.........................|
.................17--20--+
..............................................
.........................24--31--34--38--42---
.............................|.......|
.........................27--+...35--+
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MATHEMATICA
| f[n_] := (k = 1; s = {}; While[ True, k++; If[ !Divisible[n, k], AppendTo[s, k]]; If[Length[s] == 2, Break[]]]; n + Last[s]); NestList[f, 1, 58] (* From Jean-François Alcover, Oct 05 2011 *)
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CROSSREFS
| Cf. A140486-A140489.
Sequence in context: A136640 A068949 A141000 * A010397 A155563 A020684
Adjacent sequences: A140482 A140483 A140484 * A140486 A140487 A140488
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KEYWORD
| nonn
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AUTHOR
| Eric Angelini (Eric.Angelini(AT)kntv.be), Jun 25 2008
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EXTENSIONS
| More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jul 01 2008
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