

A267703


Conjectured list of numbers n such that the trajectory of n under the '7x+1' map does not cycle.


1



1, 2, 4, 5, 8, 9, 10, 16, 18, 20, 32, 36, 40, 41, 64, 72, 73, 80
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OFFSET

1,2


COMMENTS

This is conjectural in that there is no known proof that the missing numbers 3, 6, 7, ... are really missing. It may be that after after a very large number of iterations they will cycle.  N. J. A. Sloane, Jan 23 2016
Note that the computer program does not actually calculate a complete list of "numbers n such that the Collatzlike map T: if x odd, x > 7*x+1 and if x even, x > x/2, when started at n, eventually reaches 1".


LINKS

Table of n, a(n) for n=1..18.


EXAMPLE

5 is in the sequence because the trajectory of 5 is 5 > 36 > 18 > 9 > 64 > 32 > 16 > 8 > 4 > 2 > 1.


MAPLE

nn:=10000:
for n from 1 to 2340 do:
m:=n:cyc:={n}:
for i from 1 to nn do:
if irem(m, 2)=0
then
m:=m/2:
else
m:=7*m+1:
fi:
cyc:=cyc union {m}:
od:
n0:=nops(cyc):
if n0<nn
then
printf(`%d, `, n):
fi:
od :
(Warning: bad program  will not find all the terms.  N. J. A. Sloane, Jan 23 2016)


CROSSREFS

Cf. A000079, A006577, A023001, A232711, A267969, A267970.
Sequence in context: A010402 A010443 A035269 * A277075 A038558 A286031
Adjacent sequences: A267700 A267701 A267702 * A267704 A267705 A267706


KEYWORD

nonn


AUTHOR

Michel Lagneau, Jan 19 2016


EXTENSIONS

Entry revised by N. J. A. Sloane, Jan 23 2016


STATUS

approved



