A225840 Largest number less than n occurring in Collatz trajectory starting with n.

1, 2, 2, 4, 5, 5, 4, 8, 8, 10, 10, 10, 13, 10, 8, 16, 17, 17, 16, 16, 20, 20, 16, 22, 20, 23, 26, 26, 23, 23, 16, 29, 26, 20, 34, 34, 34, 38, 20, 40, 32, 40, 40, 40, 40, 46, 24, 40, 44, 44, 40, 40, 53, 53, 52, 56, 52, 58, 53, 53, 61, 61, 32, 56, 58, 58, 52

Offset

2,2

Comments

In triangle A070165: a(n)-th row is a suffix of n-th row;

a(n) = A070165(n,k) for some k with 1 <= k < A006577(n);

a(n) <> A070165(m,k) for all k with 1 <= k < A006577(n), a(n) < m < n.

Links

Reinhard Zumkeller, Table of n, a(n) for n = 2..10000

Index entries for sequences related to 3x+1 (or Collatz) problem

Mathematica

scoll[n_]:=Sort[NestWhileList[If[EvenQ[#], #/2, 3#+1]&, n, #>1&]]; Flatten[Table[scoll[n][[Flatten[Position[scoll[n], n]-1]]], {n, 2, 68}]] (* Jayanta Basu, May 28 2013 *)

Prog

(Haskell)
a225840 n = maximum $ filter (< n) $ a070165_row n

Crossrefs

Cf. A187831.

Sequence in context: A276299 A231302 A231363 * A361645 A319409 A122543

Adjacent sequences: A225837 A225838 A225839 * A225841 A225842 A225843

Keyword

nonn

Author

Reinhard Zumkeller, May 16 2013

Status

approved