%I A006781 M1788
%S A006781 1,2,7,32,168,970,5984,38786,261160,1812630,12895360,93638634
%N A006781 Number of polygons of length 4n on Manhattan lattice.
%D A006781 I. G. Enting and A. J. Guttmann, Self-avoiding polygons on the square, 
               L and Manhattan lattices, J. Phys. A 18 (1985), 1007-1017.
%D A006781 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%Y A006781 Sequence in context: A015655 A047850 A108524 this_sequence A115197 A107593 
               A125277
%Y A006781 Adjacent sequences: A006778 A006779 A006780 this_sequence A006782 A006783 
               A006784
%K A006781 nonn,walk,nice,more
%O A006781 1,2
%A A006781 N. J. A. Sloane (njas(AT)research.att.com).