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 A125709 #9 Jul 19 2020 04:05:54 %S A125709 1,5,32,444,13375,684215,52267513 %N A125709 Number of n-indecomposable polyominoes with at least n cells. %C A125709 A polyomino is called n-indecomposable if it cannot be partitioned (along cell boundaries) into two or more polyominoes each with at least n cells. %C A125709 MacKinnon incorrectly gives a(3) = 42. %C A125709 For full lists of drawings of these polyominoes for n <= 6, see the links in A125759. %H A125709 N. MacKinnon, <a href="http://www.jstor.org/stable/3618845">Some thoughts on polyomino tilings</a>, Math. Gaz., 74 (1990), 31-33. %H A125709 Simone Rinaldi and D. G. Rogers, <a href="http://www.jstor.org/stable/27821767">Indecomposability: polyominoes and polyomino tilings</a>, The Mathematical Gazette 92.524 (2008): 193-204. %e A125709 The five 2-indecomposable polyominoes: %e A125709 ...................X. %e A125709 XX..XXX..XX..XXX..XXX %e A125709 ..........X...X....X. %Y A125709 Row sums of A125753. Cf. A125759, A125761, A126742, A126743. %K A125709 nonn,more %O A125709 1,2 %A A125709 _N. J. A. Sloane_, Feb 01 2007 %E A125709 a(4) and a(5) from Peter Pleasants, Feb 13 2007 %E A125709 a(6) and a(7) from _David Applegate_, Feb 16 2007