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A207675 Numbers such that not all divisors occur in their Collatz trajectories. 3
9, 15, 18, 21, 27, 30, 33, 35, 36, 39, 42, 45, 51, 54, 55, 57, 60, 63, 66, 69, 70, 72, 75, 77, 78, 81, 84, 85, 87, 90, 91, 93, 95, 96, 99, 102, 105, 108, 110, 111, 114, 115, 117, 119, 120, 121, 123, 125, 126, 129, 132, 133, 135, 138, 140, 141, 143, 144, 145 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
Eric Weisstein's World of Mathematics, Collatz Problem
EXAMPLE
3 is a divisor of 9, not occurring in A033479 - therefore 9 is a term.
MATHEMATICA
coll[n_]:=NestWhileList[If[EvenQ[#], #/2, 3#+1]&, n, #>1&]; Select[Range[145], Complement[Divisors[#], coll[#]]!={}&] (* Jayanta Basu, May 27 2013 *)
PROG
(Haskell)
import Data.List (intersect)
a207675 n = a207675_list !! (n-1)
a207675_list = filter
(\x -> a027750_row x `intersect` a070165_row x /= a027750_row x) [1..]
CROSSREFS
Cf. A027750, A070165, A006370, A207674 (complement).
Sequence in context: A093642 A364566 A177733 * A118236 A373995 A230306
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Feb 20 2012
STATUS
approved

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Last modified July 13 14:24 EDT 2024. Contains 374284 sequences. (Running on oeis4.)