login
A225124
a(n) = least number k such that 2^n is highest in Collatz(3x+1) trajectory of k.
3
1, 2, 4, 8, 3, 32, 21, 128, 85, 512, 151, 2048, 1365, 8192, 5461, 32768, 14563, 131072, 87381, 524288, 349525, 2097152, 932067, 8388608, 5592405, 33554432, 22369621, 134217728, 26512143, 536870912, 357913941
OFFSET
0,2
EXAMPLE
a(4)=3 since 3 is the least number such that largest member of Collatz(3 x + 1) trajectory of 3 is 2^4 = 16.
MATHEMATICA
Coll[n_]:=NestWhileList[If[EvenQ[#], #/2, 3*#+1]&, n, #>1 &]; t={}; Do[i=1; While[Max[Coll[i]] != 2^n, i++]; AppendTo[t, i], {n, 0, 25}]; t
PROG
(Haskell)
a225124 = (+ 1) . fromJust . (`elemIndex` a025586_list) . a000079
-- Reinhard Zumkeller, Apr 30 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Jayanta Basu, Apr 29 2013
STATUS
approved