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A207674 Numbers such that all divisors occur in their Collatz trajectories. 4
1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 16, 17, 19, 20, 22, 23, 24, 25, 26, 28, 29, 31, 32, 34, 37, 38, 40, 41, 43, 44, 46, 47, 48, 49, 50, 52, 53, 56, 58, 59, 61, 62, 64, 65, 67, 68, 71, 73, 74, 76, 79, 80, 82, 83, 86, 88, 89, 92, 94, 97, 98, 100, 101 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

Eric Weisstein's World of Mathematics, Collatz Problem

Wikipedia, Collatz conjecture

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

MATHEMATICA

coll[n_]:=NestWhileList[If[EvenQ[#], #/2, 3#+1]&, n, #>1&]; Select[Range[101], Complement[Divisors[#], coll[#]]=={}&] (* Jayanta Basu, May 27 2013 *)

PROG

(Haskell)

import Data.List (intersect)

a207674 n = a207674_list !! (n-1)

a207674_list = filter

   (\x -> a027750_row x `intersect` a070165_row x == a027750_row x) [1..]

CROSSREFS

Cf. A027750, A070165, A006370, A207675 (complement), A000079 and A000040 are subsequences.

Sequence in context: A331914 A324935 A328369 * A162722 A123345 A093641

Adjacent sequences:  A207671 A207672 A207673 * A207675 A207676 A207677

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Feb 20 2012

STATUS

approved

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Last modified July 30 12:39 EDT 2021. Contains 346359 sequences. (Running on oeis4.)