%I A123837
%S A123837 1,1,1,4,7,10,13,61,154,256
%N A123837 Number of ways to build a contiguous building with n LEGO blocks of size 
               3 X 3 on top of a fixed block of the same size so that the building 
               is symmetric after a rotation by 90 degrees.
%C A123837 The base block is not counted among the n and must be the only block 
               in the bottom layer of the building
%D A123837 M. Abrahamsen and S. Eilers, Efficient counting of LEGO buildings, in 
               preparation
%D A123837 B. Durhuus and S. Eilers, On the entropy of LEGO, arXiv:math.CO/0504039
%H A123837 S. Eilers, <a href="http://www.math.ku.dk/~eilers/lcounts.html">LEGO 
               counts</a>
%Y A123837 Sequence in context: A119256 A143454 A065810 this_sequence A125620 A062389 
               A080600
%Y A123837 Adjacent sequences: A123834 A123835 A123836 this_sequence A123838 A123839 
               A123840
%K A123837 nonn
%O A123837 1,4
%A A123837 Soren Eilers (eilers(AT)math.ku.dk), Oct 29 2006