OFFSET
1,2
COMMENTS
It seems that a(n)/n > 3 for all n > 40.
This sequence is not a permutation of the natural numbers.
LINKS
Alois P. Heinz Table of n, a(n) for n = 1..5000
Eric Angelini, Colour, drag and drop sequence
E. Angelini, Colour, drag and drop sequence [Cached copy, with permission]
MAPLE
mx:= 300: # increase mx to get more items
l:= [i$i=1..3*mx]: pos:= proc(n) global l; local i; for i to nops(l) while l[i]<>n do od; `if`(i>nops(l), -1, i) end: for n from 1 to mx do p:= pos(n); l:= [l[1..p][], l[n+p], l[p+1..n+p-1][], l[n+p+1..nops(l)][]] od: for p to nops(l) do if l[p]>=mx then break fi od: a:= n-> `if`(n<p, l[n], NULL): seq(a(n), n=1..p);
MATHEMATICA
max = 900; r = Range[max]; For[n = 1, True, n++, p = Position[r, n]; If[p == {} || p[[1, 1]] + n > max, Break[], c = r[[p[[1, 1]] + n]]; r = r /. {a___, n, b___, c, d___} :> {a, n, c, b, d}]]; A164286 = r[[1 ;; 61]] (* Jean-François Alcover, Jun 14 2012 *)
CROSSREFS
KEYWORD
nice,nonn
AUTHOR
Eric Angelini and Alois P. Heinz, Aug 12 2009
STATUS
approved