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 A217990 #22 Nov 07 2023 03:16:02 %S A217990 1,2,5,10,17,26,37,50,65,82,101,122,145,170,197,226,257,290,420 %N A217990 Size of largest semigroup generated by one Boolean n X n matrix. %D A217990 J. Denes, K. H. Kim, and F. W. Roush, Automata on one symbol, in Studies in Pure Mathematics: To the Memory of Paul Turan, Birkhäuser, 1983, pp. 127-134. %H A217990 George Markowsky, <a href="https://eudml.org/doc/134218">Bounds on the index and period of a binary relation on a finite set</a>, Semigroup Forum 13 (1977), 253-259. %F A217990 For n < 19, a(n) = n^2 - 2n + 2. For large n, l(n) <= a(n) < n^2 - 2n + 2 + l(n), where l(n) is Landau's function (A000793). It seems the exact value is still unknown. %e A217990 a(4) = 10: the matrix [[0,0,0,1], [0,0,1,0], [1,0,0,0], [0,1,1,0]] generates a semigroup of order 10 under Boolean matrix multiplication. %Y A217990 Cf. A000793, A202140. %K A217990 nonn,hard,more %O A217990 1,2 %A A217990 _Jeffrey Shallit_, Oct 17 2012