Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #3 Mar 31 2012 12:35:09
%S 1,1,3,3,9,11,82,254,1669,6665,68316,226521,4561686,23734103,
%T 704383992,5907579541,236178663400,2337315883467,150056765859689,
%U 1811327966926780,189399759509400492,3276661629995792339,507766610202105772758
%N Number of n X n binary arrays symmetric under horizontal reflection with all ones connected only either as two by three or three by two blocks.
%e Maximal 8 X 8 example
%e .1.1.1.0.0.1.1.1
%e .1.1.1.0.0.1.1.1
%e .0.0.0.0.0.0.0.0
%e .1.1.1.0.0.1.1.1
%e .1.1.1.0.0.1.1.1
%e .0.0.0.0.0.0.0.0
%e .1.1.1.0.0.1.1.1
%e .1.1.1.0.0.1.1.1
%K nonn
%O 1,3
%A _R. H. Hardin_, Oct 27 2008