%I A057424
%S A057424 1,1,5,7,21,30,88,116,336
%N A057424 Diagonally symmetric (about diagonal 2) 2n-celled polyominoes with 1 
               hole.
%H A057424 Tomas Oliveira e Silva, <a href="http://www.ieeta.pt/~tos/animals.html">
               Enumeration of polyominoes</a>
%Y A057424 Sequence in context: A117321 A120035 A091154 this_sequence A027152 A076197 
               A002596
%Y A057424 Adjacent sequences: A057421 A057422 A057423 this_sequence A057425 A057426 
               A057427
%K A057424 nonn
%O A057424 6,3
%A A057424 N. J. A. Sloane (njas(AT)research.att.com), Sep 05 2000