The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A231334 Lexicographically earliest sequence of distinct positive integers such that for any distinct i,j, k, the points at positions (i, a(i)), (j, a(j)), (k, a(k)) are not aligned. 8
 1, 2, 4, 3, 6, 5, 9, 12, 7, 14, 13, 8, 23, 17, 18, 22, 10, 15, 11, 28, 19, 16, 20, 29, 32, 44, 35, 39, 24, 40, 26, 37, 42, 21, 56, 64, 43, 31, 25, 34, 27, 33, 66, 67, 52, 60, 30, 57, 36, 63, 86, 82, 38, 50, 47, 69, 75, 79, 89, 49, 45, 76, 41, 48, 98, 77, 94 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Is this a permutation of the natural numbers? There are only two fixed points: 1 and 2. LINKS Paul Tek, Table of n, a(n) for n = 1..10000 Paul Tek, C program for this sequence Illustrations of the first 200 points at positions (n, a(n)) (black pixels correspond to these points, colored pixels (x,y) are aligned with two black pixels (i,a(i)) and (j,a(j))): (1) x < i < j, (2) i < x < j, (3) i < j < x. MATHEMATICA WIDTH = 1000; HEIGHT = 2000; Clear[seen, aligned, a]; compute[n_] := Module[{c = 1}, While[seen[c] || aligned[n][c], c++; If[c > HEIGHT, Abort[]]]; a[n] = c; seen[a[n]] = True; For[i = 1, i < n, i++, dn = n - i; da = a[n] - a[i]; g = GCD[dn, da]; dn /= g; da /= g; nn = n; na = c; While[True, nn += dn; If[nn > WIDTH, Break[]]; na += da; If[na < 1 || na > HEIGHT, Break[]]; aligned[nn][na] = True]]; a[n]]; Array[compute, WIDTH] (* Jean-François Alcover, Apr 19 2020, translated from Paul Tek's program. *) PROG (C) See Link section. CROSSREFS Cf. A175498, A236266, A236335, A300002. Sequence in context: A113321 A271647 A232643 * A253609 A300002 A082560 Adjacent sequences:  A231331 A231332 A231333 * A231335 A231336 A231337 KEYWORD nonn AUTHOR Paul Tek, Nov 07 2013 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified July 29 17:41 EDT 2021. Contains 346346 sequences. (Running on oeis4.)