2,1

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

S. G. Whittington and J. P. Valleau, Figure eights on the square lattice: enumeration and Monte Carlo estimation, J. Phys. A 3 (1970), 21-27.

Sequence in context: A150863 A084137 A129400 this_sequence A150864 A054116 A131785

Adjacent sequences: A003301 A003302 A003303 this_sequence A003305 A003306 A003307

nonn

N. J. A. Sloane (njas(AT)research.att.com).