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A064419
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a(n) = n for n <= 5; for n > 5, a(n) = smallest number not already used such that GCD{ a(n), a(n-1) } >= 5.
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3
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1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 6, 12, 18, 9, 27, 36, 24, 8, 16, 32, 40, 35, 7, 14, 21, 28, 42, 48, 54, 45, 50, 55, 11, 22, 33, 44, 66, 60, 65, 13, 26, 39, 52, 78, 72, 56, 49, 63, 70, 75, 80, 64, 88, 77, 84, 90, 81, 99, 108, 96, 102, 17, 34, 51, 68, 85, 95, 19, 38, 57, 76, 114, 120
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| A permutation of the natural numbers.
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LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
J. C. Lagarias, E. M. Rains and N. J. A. Sloane, The EKG sequence, Exper. Math. 11 (2002), 437-446.
Index entries for sequences related to EKG sequence
Index entries for sequences that are permutations of the natural numbers
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PROG
| (Haskell)
a064419 n = a064419_list !! (n-1)
a064419_list = [1, 2, 3, 4, 5] ++ f 5 [] [6..] where
f z xs (y:ys) | y `gcd` z > 4 = y : f y [] (reverse xs ++ ys)
| otherwise = f z (y:xs) ys
-- Reinhard Zumkeller, Sep 17 2001
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CROSSREFS
| Cf. A064413. See A064959 for inverse permutation.
Sequence in context: A074821 A076707 A032940 * A032543 A140730 A205962
Adjacent sequences: A064416 A064417 A064418 * A064420 A064421 A064422
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KEYWORD
| nonn,nice,easy
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AUTHOR
| Jonathan Ayres (Jonathan.ayres(AT)btinternet.com), Sep 30 2001
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EXTENSIONS
| More terms from Naohiro Nomoto (n_nomoto(AT)yabumi.com), Sep 30 2001
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