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 A333313 #19 Jun 20 2024 14:47:27 %S A333313 1,1,1,2,3,7,13,30,64,150,338,794,1836,4313,10067,23621,55313,129647, %T A333313 303720,711078,1665037,3894282,9111343,21290577,49770844,116206114, %U A333313 271435025,633298969,1478178004,3446626028,8039424324,18734704111,43673728357,101723730306 %N A333313 Number of 2-sided strip polyominoes with n cells and no holes. %C A333313 This sequence first differs from A002013 at n = 7. An example of a polyomino counted by A002013, but not by this sequence, is: %C A333313 ### %C A333313 # # %C A333313 ## %H A333313 Code Golf Stack Exchange, <a href="https://codegolf.stackexchange.com/q/155983/53884">Counting polystrips</a> %H A333313 Arthur O'Dwyer, <a href="https://quuxplusone.github.io/blog/2022/12/08/polyomino-snakes/">Polyomino strips, snakes, and ouroboroi</a>, 2022. %Y A333313 Cf. A002013. %K A333313 nonn %O A333313 0,4 %A A333313 _Peter Kagey_, Mar 14 2020 %E A333313 a(16)-a(26) from _John Mason_, Sep 15 2022 %E A333313 a(27)-a(33) from Arthur O'Dwyer's blog added by _Andrey Zabolotskiy_, Jun 20 2024