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 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 (list; graph; refs; listen; history; text; internal format)
 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 n such that the Collatz-like map T: if x odd, x -> 7*x+1 and if x even, x -> x/2, when started at n, eventually reaches 1". LINKS 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

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Last modified December 6 22:25 EST 2021. Contains 349567 sequences. (Running on oeis4.)