This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A007275 M4223 #15 Dec 05 2017 10:14:05 %S A007275 1,6,36,216,1296,7776,46440,276054,1633848,9633366,56616132,331847118, %T A007275 1940715960,11327957196,66010769382,384094025382,2231978658906 %N A007275 Walks on hexagonal lattice using each point at most three times. %C A007275 The hexagonal lattice is the familiar 2-dimensional lattice in which each point has 6 neighbors. This is sometimes called the triangular lattice. %C A007275 Guttmann et al. has incorrect a(10) = 56616140, a(11) = 331847200, and a(12) = 1940717000. - _Sean A. Irvine_, Dec 03 2017 %D A007275 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A007275 A. J. Guttmann, C. Byrnes and N. E. Frankel, <a href="https://doi.org/10.1088/0305-4470/17/9/001">A generalized self-avoiding walk</a>, J. Phys. A 17 (1984), L457-L461. %H A007275 G. Nebe and N. J. A. Sloane, <a href="http://www.math.rwth-aachen.de/~Gabriele.Nebe/LATTICES/A2.html">Home page for hexagonal (or triangular) lattice A2</a> %Y A007275 Cf. A001334, A007274. %K A007275 nonn,walk %O A007275 0,2 %A A007275 _Simon Plouffe_ %E A007275 Title improved, a(10)-a(12) corrected, and a(15)-a(16) added by _Sean A. Irvine_, Dec 03 2017