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%I A230627 #72 Aug 04 2023 01:39:38
%S A230627 2,3,31,5,11,7,11,23,31,11,43,13,23,29,251,17,23,19,251,31,43,23,47,
%T A230627 43,463,29,23,29,127,31,31,59,23,47,8093,37,83,61,127,41,179,43,467,
%U A230627 463,23,47,83,127,467,113,173,53,47,23,179,241,127,59,349,61,179
%N A230627 Prime reached in A230626, or -1 if no prime is reached.
%C A230627 _David J. Seal_ found that the number 255987 is fixed by the map described in A230625 (or equally A287874), so a(255987) = -1. - _N. J. A. Sloane_, Jun 15 2017
%C A230627 I also observe that the numbers 1007 and 1269 are mapped to each other by that map, as are the numbers 1503 and 3751 (see the b-file submitted by _Chai Wah Wu_ for A230625). So a(1007) = a(1269) = a(1503) = a(3751) = -1. - _David J. Seal_, Jun 16 2017
%C A230627 a(217) = a(255) = a(446) = a(558) = a(717) = a(735) = a(775) = a(945) = a(958) = -1 since the trajectory either converges to (1007,1269) or to (1503,3751). - _Chai Wah Wu_, Jun 16 2017
%C A230627 See A287878 for the trajectory of 234. - _N. J. A. Sloane_, Jun 17 2017
%C A230627 See A288894 for the trajectory of 3932. - _Sean A. Irvine_, Jun 18 2017
%C A230627 The latest information seems to be that for numbers less than 12388, all trajectories either end at a fixed point or in a cycle of length 2. - _N. J. A. Sloane_, Jul 27 2017
%H A230627 Sean A. Irvine, <a href="/A230627/b230627.txt">Table of n, a(n) for n = 2..10000</a> (terms 2..3931 from Chai Wah Wu)
%H A230627 N. J. A. Sloane, <a href="/A195264/a195264.pdf">Confessions of a Sequence Addict (AofA2017)</a>, slides of invited talk given at AofA 2017, Jun 19 2017, Princeton. Mentions this sequence.
%H A230627 N. J. A. Sloane, Three (No, 8) Lovely Problems from the OEIS, Experimental Mathematics Seminar, Rutgers University, Oct 05 2017, <a href="https://vimeo.com/237029685">Part I</a>, <a href="https://vimeo.com/237030304">Part 2</a>, <a href="https://oeis.org/A290447/a290447_slides.pdf">Slides.</a> (Mentions this sequence)
%t A230627 fn[n_] := FromDigits[Flatten[IntegerDigits[ReplaceAll[FactorInteger[n], {x_, 1} -> {x}], 2]], 2];
%t A230627 Table[NestWhile[fn, n, # != 1 && ! PrimeQ[#] &], {n, 2, 50}] (* _Robert Price_, Mar 16 2020 *)
%Y A230627 Base-2 analog to A195264.
%Y A230627 Cf. A230625, A230626, A287878.
%Y A230627 See A287875 for these same numbers written in binary.
%Y A230627 See A288847 for where the values -1 occur.
%K A230627 sign,base
%O A230627 2,1
%A A230627 _N. J. A. Sloane_, Oct 27 2013
%E A230627 More terms from _Chai Wah Wu_, Jul 15 2014
%E A230627 Changed the "escape" value from 0 to -1 to be consistent with A195264. - _N. J. A. Sloane_, Jul 27 2017

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