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 A006770 M3565 #39 Jul 08 2025 16:54:32 %S A006770 1,4,20,110,638,3832,23592,147941,940982,6053180,39299408,257105146, %T A006770 1692931066,11208974860,74570549714,498174818986,3340366308393 %N A006770 Number of fixed n-celled polyominoes which need only touch at corners. %C A006770 Also known as fixed polyplets. - _David Bevan_, Jul 28 2009 %D A006770 D. H. Redelmeier, personal communication. %D A006770 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A006770 M. F. Hasler, <a href="/A006770/a006770.png">Illustration of the A006770(3)=20 fixed 3-polyplets</a>, Sep 29 2014. %H A006770 S. Mertens, <a href="http://dx.doi.org/10.1007/BF01026565">Lattice animals: a fast enumeration algorithm and new perimeter polynomials</a>, J. Stat. Phys. 58 (5-6) (1990) 1095-1108, Table 1. %H A006770 H. Redelmeier, <a href="/A006770/a006770.pdf">Emails to N. J. A. Sloane, 1991</a> %H A006770 Hugo Tremblay and Julien Vernay, <a href="https://doi.org/10.1051/ita/2024013">On the generation of discrete figures with connectivity constraints</a>, RAIRO-Theor. Inf. Appl. (2024) Vol. 58, Art. No. 16. See p. 13. %H A006770 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Polyplet.html">Polyplet.</a> %H A006770 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pseudo-polyomino">Pseudo polyomino</a> %e A006770 a(2)=4: the two fixed dominoes and the two rotations of the polyplet consisting of two cells touching at a vertex. - _David Bevan_, Jul 28 2009 %e A006770 a(3)=20 counts 4 rotations (by 0°, 45°, 90°, 135°) of the straight ... trinomino, and 8 rotations (by multiples of 45°) of the L-shaped .: trinomino and the ..· 3-polyplet, cf. link to the image. - _M. F. Hasler_, Sep 30 2014 %Y A006770 Cf. A030222 (free polyplets). %Y A006770 10th row of A366767. %K A006770 nonn,hard,more %O A006770 1,2 %A A006770 _N. J. A. Sloane_ %E A006770 One more term from _Joseph Myers_, Sep 26 2002