OFFSET
1,6
COMMENTS
An isolated even is not a member of any even chain in Collatz trajectory of n; see also A213181.
LINKS
T. D. Noe, Table of n, a(n) for n = 1..10000
EXAMPLE
a(7)=2 since there are only 2 numbers 22 and 34 in the Collatz trajectory of 7 that are not part of any even chain.
MATHEMATICA
Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; Table[c = Collatz[n]; cnt = 0; evenCnt = 0; Do[If[OddQ[i], If[evenCnt == 1, cnt++]; evenCnt = 0, evenCnt++], {i, c}]; cnt, {n, 100}] (* T. D. Noe, Mar 02 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jayanta Basu, Mar 02 2013
STATUS
approved