A225124 a(n) = least number k such that 2^n is highest in Collatz(3x+1) trajectory of k.

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

Links

Table of n, a(n) for n=0..30.

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

Cf. A000079, A025586, A095381, A231610.

Sequence in context: A332306 A223699 A231610 * A344537 A349104 A059884

Adjacent sequences: A225121 A225122 A225123 * A225125 A225126 A225127

Keyword

nonn

Author

Jayanta Basu, Apr 29 2013

Status

approved