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 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 k such that the Collatz-like map T: if x odd, x -> 7*x+1 and if x even, x -> x/2, when started at k, eventually reaches 1".
LINKS
Dmitry Kamenetsky, Table of n, a(n) for n = 1..164
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
KEYWORD
nonn
AUTHOR
Michel Lagneau, Jan 19 2016
EXTENSIONS
Entry revised by N. J. A. Sloane, Jan 23 2016
a(19)-a(55) from Dmitry Kamenetsky, Jun 24 2024
STATUS
approved