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A207675
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Numbers such that not all divisors occur in their Collatz trajectories.
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3
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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
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OFFSET
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1,1
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LINKS
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EXAMPLE
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3 is a divisor of 9, not occurring in A033479 - therefore 9 is a term.
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MATHEMATICA
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coll[n_]:=NestWhileList[If[EvenQ[#], #/2, 3#+1]&, n, #>1&]; Select[Range[145], Complement[Divisors[#], coll[#]]!={}&] (* Jayanta Basu, May 27 2013 *)
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PROG
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(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..]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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