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 A143691 Lexicographically earliest permutation of the natural numbers having alternating even and odd numbers of prime factors. 6
 1, 2, 4, 3, 6, 5, 9, 7, 10, 8, 14, 11, 15, 12, 16, 13, 21, 17, 22, 18, 24, 19, 25, 20, 26, 23, 33, 27, 34, 28, 35, 29, 36, 30, 38, 31, 39, 32, 40, 37, 46, 41, 49, 42, 51, 43, 54, 44, 55, 45, 56, 47, 57, 48, 58, 50, 60, 52, 62, 53, 64, 59, 65, 61, 69, 63, 74, 66, 77, 67, 81, 68 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A066829(a(n)*a(n+1)) = 1; n mod 2 + A001222(a(n)) = 1; a(2*n) = A026424(n); a(2*n-1) = A028260(n); a(a(n)) = A143693(n). LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 Index entries for sequences that are permutations of the natural numbers PROG (Haskell) import Data.List (delete) a143691 n = a143691_list !! (n-1) a143691_list = f 1 [1..] where f m xs = g xs where g (z:zs) = if m + m' /= 1 then g zs else z : f m' (delete z xs) where m' = a001222 z `mod` 2 -- Reinhard Zumkeller, Aug 07 2014 CROSSREFS Cf. A143692 (inverse), A001222, A066829, A026424, A028260, A143693, A109465. Sequence in context: A354453 A281120 A246682 * A129767 A119618 A113321 Adjacent sequences: A143688 A143689 A143690 * A143692 A143693 A143694 KEYWORD nonn AUTHOR Reinhard Zumkeller, Aug 29 2008 STATUS approved

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Last modified December 10 04:38 EST 2023. Contains 367699 sequences. (Running on oeis4.)