A022445 Number of self-avoiding closed walks (from 0 to 0) of length 2n in the strip {0, 1, 2} X Z of the square lattice Z X Z.

1, 0, 4, 10, 34, 94, 222, 516, 1202, 2738, 6110, 13496, 29586, 64350, 139006, 298636, 638578, 1359754, 2884638, 6099552, 12859730, 27040694, 56723774, 118732340, 248034354, 517208034, 1076694622, 2237946376, 4645007122

Offset: 0

Author

Jacques Labelle (labelle.jacques(AT)uqam.ca)

Keywords

• nonn
• walk
• easy

References

• J. Labelle, Self-avoiding walks and polyominoes in strips, Bull. ICA, 23 (1998), 88-98.

Formula

G.f.: (-6*x^7+10*x^6-18*x^5+27*x^4-14*x^3+10*x^2-4*x+1) / ((1+x^2)^2*(1-2*x)^2) (conjectured). - Ralf Stephan, Apr 28 2004

Extensions

More terms from Sean A. Irvine, May 16 2019