cp's OEIS Frontend

A140485 Trajectory of 1 under repeated application of the map: n -> n + second-smallest number that does not divide n.

%I A140485 #15 Jun 30 2021 16:01:42
%S A140485 1,4,9,13,16,21,25,28,33,37,40,46,50,54,59,62,66,71,74,78,83,86,90,97,
%T A140485 100,106,110,114,119,122,126,131,134,138,143,146,150,157,160,166,170,
%U A140485 174,179,182,186,191,194,198,203,206,210,218,222,227,230,234,239,242,246
%N A140485 Trajectory of 1 under repeated application of the map: n -> n + second-smallest number that does not divide n.
%e A140485 The numbers that do not divide 4 are 3, 5, 6, 7, ..., so a(3) = 4+5 = 9.
%e A140485 Here are the beginnings of the trajectories of some small numbers:
%e A140485 ...1--4--9---13--16--21--25--28--32--37--40---
%e A140485 .............|...................|...|
%e A140485 ......5--8---+...............29--+...|
%e A140485 .....................................|
%e A140485 ...2--6--11--14--18--23--26--30------+
%e A140485 .............|...........|...........|
%e A140485 ...3--7--10--+...........|.......33--+
%e A140485 .........................|
%e A140485 .............12--19--22--+
%e A140485 .................|.......|
%e A140485 .............15--+.......|
%e A140485 .........................|
%e A140485 .................17--20--+
%e A140485 ..............................................
%e A140485 .........................24--31--34--38--42---
%e A140485 .............................|.......|
%e A140485 .........................27--+...35--+
%t A140485 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] (* _Jean-François Alcover_, Oct 05 2011 *)
%t A140485 NestList[#+Complement[Range[100],Divisors[#]][[2]]&,1,60] (* _Harvey P. Dale_, Apr 27 2012 *)
%Y A140485 Cf. A140486, A140487, A140488, A140489, A140595.
%K A140485 nonn
%O A140485 1,2
%A A140485 _Eric Angelini_, Jun 25 2008
%E A140485 More terms from _Stefan Steinerberger_, Jul 01 2008