%I
%S 1,2,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,15,
%T 15,16,16,17,17,18,18,19,19,20,20,21,21,22,22,23,23,24,24,25,25,26,26,
%U 27,27,28,28,29,29,30,30,31,31,32,32,33
%N Sequence of block lengths in a block spiral of width 1.
%C A lefthanded block spiral is created by the following pattern: Start with a 1 X 1 square [ a(1)=1 ]. Attach a block of length 2 and width 1 (a horizontal 1 X 2 rectangle) to the upper side of the square [ a(2)=2 ] pointing to the right. Attach to the corner a vertical 2 X 1 block (rectangle). This block has length 2, so a(3)=2. Continue with a horizontal 1 X 2 block, so a(4) = 2. And so on. See the sketch shown in the link.
%H Hans G. Oberlack, <a href="/A263997/a263997.pdf">Sketch of a block spiral</a>
%F a(n) = a(n2) + 1 for n > 4.
%F O.g.f.: x*(1+xx^2x^3+x^4)/((1x)*(1x^2)). From A008619.  _Wolfdieter Lang_, Jan 05 2016
%Y Essentially the same as A008619.
%K nonn,easy
%O 1,2
%A _Hans G. Oberlack_, Oct 31 2015
%E Edited by _Wolfdieter Lang_, Jan 05 2016
