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A187763 Number of common terms in consecutive Collatz trajectories. 1
1, 2, 3, 3, 6, 7, 4, 4, 7, 7, 7, 7, 10, 9, 5, 5, 13, 16, 8, 5, 5, 9, 7, 7, 11, 9, 9, 16, 9, 17, 5, 5, 14, 9, 9, 19, 16, 22, 9, 9, 5, 5, 16, 14, 9, 17, 7, 7, 16, 20, 12, 9, 12, 106, 9, 20, 16, 20, 9, 17, 20, 95, 5, 5, 16, 23, 14, 12, 9, 15, 9, 9, 9, 5, 5, 20 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Size of intersection of row n and row n+1 in A070165.

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

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

EXAMPLE

.                                | Rows in A070165 (trajectories)

a(1) = #{1} = 1;                 | 1

a(2) = #{2,1} = 2;               | 2,1

a(3) = #{4,2,1} = 3;             | 3,10,5,16,8,4,2,1

a(4) = #{4,2,1} = 3;             | 4,2,1

a(5) = #{5,16,8,4,2,1} = 6;      | 5,16,8,4,2,1

a(6) = #{10,5,16,8,4,2,1} = 7;   | 6,3,10,5,16,8,4,2,1

a(7) = #{8,4,2,1} = 4;           | 7,22,11,34,17,52,26,13,40,20,10,5,..

a(8) = #{8,4,2,1} = 4;           | 8,4,2,1

a(9) = #{10,5,16,8,4,2,1} = 7;   | 9,28,14,7,22,11,34,17,52,26,13,40,..

a(10) = #{10,5,16,8,4,2,1} = 7;  | 10,5,16,8,4,2,1

a(11) = #{10,5,16,8,4,2,1} = 7;  | 11,34,17,52,26,13,40,20,10,5,16,8,4,..

a(12) = #{10,5,16,8,4,2,1} = 7.  | 12,6,3,10,5,16,8,4,2,1

.                                | 13,40,20,10,5,16,8,4,2,1 .

MATHEMATICA

coll[n_]:=NestWhileList[If[EvenQ[#], #/2, 3#+1]&, n, #>1&]; Table[Length[Intersection[coll[n], coll[n+1]]], {n, 76}] (* Jayanta Basu, May 28 2013 *)

PROG

(Haskell)

import Data.List (intersect)

a187763 n = a187763_list !! (n-1)

a187763_list = map length $

               zipWith intersect a070165_tabf $ tail a070165_tabf

CROSSREFS

Sequence in context: A143715 A159685 A251729 * A187262 A117670 A181695

Adjacent sequences:  A187760 A187761 A187762 * A187764 A187765 A187766

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jan 04 2013

STATUS

approved

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Last modified September 23 15:06 EDT 2020. Contains 337310 sequences. (Running on oeis4.)