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
n = greatest common divisor of row n. - Reinhard Zumkeller, Nov 30 2015
LINKS
R. Zumkeller, Table of n, a(n) for n = 1..10000 - Reinhard Zumkeller, Jun 22 2009
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
AUTHOR
Amarnath Murthy, Sep 22 2002
EXTENSIONS
More terms from Sascha Kurz, Jan 28 2003
STATUS
approved