%I #3 Mar 31 2012 13:46:51
%S 2,1,2,1,1,2,1,2,1,1,1,2,2,1,1,1,1,2,2,2,1,1,1,1,1,1,2,1,2,2,2,2,1,1,
%T 1,1,1,1,1,1,2,1,1,2,2,1,2,2,2,1,2,1,2,1,1,1,1,1,1,1,1,2,1,1,1,1,2,1,
%U 2,2,1,1,2,2,2,2,1,2
%N A simple "Fractal Jump Sequence" (FJS).
%C See A105397 for definition of Fractal Jump Sequence.
%C This is how to construct the sequence: start with 2 on rows a and b; put 2 empty spaces behind the 2 on row a; choose any two digits and put them on row b under the 2 empty spaces of row a; go back to row a and add the same two digits but each one with its according spaces (1 must always be followed by 1 space on row a and 2 must always be followed by 2 spaces); go back to row b and add under the next available spaces of a the digits necessary so to have the same succession of digits in rows b and a. The sequence builds itself automatically. The row (c) is obtained by "pushing" (a) into (b) -- [the first digit of a and b melt in a single copy of themselves]. Row (c) is the FJS sequence above.
%C (a)..2..1.2..1.1.2..1.2..1.1.1.2..2.....
%C (b)..212.1.12.1.2.11.1.22.1.1.1.12.22...
%C ----------------------------------------
%C (c)..21211212111221111222111111212222...
%e To build such sequences one has only to choose the first digit d and the d digits to put under the d spaces of row (a).
%K base,easy,nonn
%O 2,1
%A _Eric Angelini_, May 04 2005