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 A354850 #16 Aug 12 2022 12:38:23 %S A354850 1,3,21,59,198,703,2568,8421,26165,78074,229881,668082,1928220, %T A354850 5523946,15745682,44666804,126251748,355692380,999498933,2802212026, %U A354850 7841587533,21907928927,61123152811,170333279738,474197771123,1319004492132,3666181193067,10183729521212 %N A354850 a(n) is the number of free polyominoes of width 4 and size n. %C A354850 The sequence can be generated using a series of recursive formulas in a fashion similar to A352720 and A353067. These require respectively around 500 and 62000 formula lines, whereas a(n) requires about 10 million lines. %H A354850 John Mason, <a href="/A354850/b354850.txt">Table of n, a(n) for n = 4..100</a> %H A354850 John Mason, <a href="/A354850/a354850.txt">Java programs for calculating sequence, valid also for widths 2 and 3</a> %Y A354850 Cf. A000105, A352720, A353067. %K A354850 nonn %O A354850 4,2 %A A354850 _John Mason_, Jun 08 2022