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A075383 Rearrangement of natural numbers so that next n numbers are each divisible by n. 18
1, 2, 4, 3, 6, 9, 8, 12, 16, 20, 5, 10, 15, 25, 30, 18, 24, 36, 42, 48, 54, 7, 14, 21, 28, 35, 49, 56, 32, 40, 64, 72, 80, 88, 96, 104, 27, 45, 63, 81, 90, 99, 108, 117, 126, 50, 60, 70, 100, 110, 120, 130, 140, 150, 160, 11, 22, 33, 44, 55, 66, 77, 121, 132, 143, 154, 84 (list; table; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Integer permutation with inverse A096780: a(A096780(n))=A096780(a(n))=n; A096781(n) = a(a(n)). - Reinhard Zumkeller, Jul 09 2004
Primes occur in natural order: a(A072205(n)) = A000040(n). - Reinhard Zumkeller, Jun 22 2009
n = greatest common divisor of row n. - Reinhard Zumkeller, Nov 30 2015
LINKS
EXAMPLE
1;
2, 4;
3, 6, 9;
8, 12, 16, 20;
5, 10, 15, 25, 30;
18, 24, 36, 42, 48, 54;
7, 14, 21, 28, 35, 49, 56;
32, ...
MATHEMATICA
row[1] = {1}; row[n_] := row[n] = (For[rows = Join[row /@ Range[n-1]]; ro = {}; k = n, Length[ro] < n, k = k+n, If[FreeQ[rows, k], AppendTo[ro, k]]]; ro); Array[row, 12] // Flatten (* Jean-François Alcover, Apr 28 2017 *)
PROG
(Haskell)
import Data.List ((\\))
a075383 n k = a075383_tabl !! (n-1) !! (k-1)
a075383_row n = a075383_tabl !! (n-1)
a075383_tabl = f 1 [1..] where
f x zs = ys : f (x + 1) (zs \\ ys) where
ys = take x $ filter ((== 0) . (`mod` x)) zs
a075383_list = concat a075383_tabl
-- Reinhard Zumkeller, Nov 30 2015
CROSSREFS
Cf. A000040, A072205, A096780, A096781, A263896 (central terms).
Sequence in context: A331018 A054428 A095167 * A338919 A348018 A363504
KEYWORD
nonn,tabl,look,easy
AUTHOR
Amarnath Murthy, Sep 22 2002
EXTENSIONS
More terms from Sascha Kurz, Jan 28 2003
STATUS
approved

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Last modified March 19 03:33 EDT 2024. Contains 370952 sequences. (Running on oeis4.)