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 A209412 #7 Mar 30 2012 18:40:59 %S A209412 1,5,188,3684030417 %N A209412 Number of nonisomorphic semigroups of order 2^n. %C A209412 This is to A000679 as semigroups are to groups. %F A209412 a(n) = A027851(A000079(n)). %e A209412 a(3) = 3684030417 because there are 3684030417 nonisomorphic semigroups of order 2^3 = 8. %Y A209412 Cf. A000079, A000679 Number of groups of order 2^n, A027851 Number of nonisomorphic semigroups of order n. %K A209412 nonn,hard %O A209412 0,2 %A A209412 _Jonathan Vos Post_, Mar 08 2012