|
|
A355240
|
|
Numbers of steps until the Collatz iteration started at k > 4 returns to either k-1 or k+1.
|
|
5
|
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
It is conjectured that no further terms exist.
Michael S. Branicky checked this up to 2*10^9 and found no starting values other than the 74 terms given in A355239 and also in the attached file.
The terms of this sequence are expected to be close to the sum of numerators and denominators in a rational approximation of log(2)/log(3). See A355514, which shares terms 3, 8, 13, 44, 75.
|
|
LINKS
|
|
|
PROG
|
(PARI) a355240(upto) = {my(D=List()); for (start=5, upto, my(old=start, new=0, L=0); while (abs(new-start)>1 && new!=1, L++; if(old%2==0, new=old/2, new=3*old+1); old=new); if(new>1, listput(~D, L))); Set(D)};
a355240(10000)
|
|
CROSSREFS
|
A355239 gives the list of starting values.
|
|
KEYWORD
|
nonn,more
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|