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 A114491 #5 Aug 08 2015 23:58:33 %S A114491 2,3,6,17,69,407,3808,75165,10607541 %N A114491 Number of "ultrasweet" Boolean functions of n variables. %C A114491 A Boolean function is ultrasweet if it is sweet (see A114302) under all permutations of the variables. %C A114491 Two students, Shaddin Dughmi and Ian Post, have identified these functions as precisely the monotone Boolean functions whose prime implicants are the bases of a matroid, together with the constant function 0. This explains why a(n) = A058673(n) + 1. %e A114491 For all n>1, a function like "x2" is counted in the present sequence but not in A114572. %Y A114491 Cf. A114302, A114303, A114572, A058673. %K A114491 nonn %O A114491 0,1 %A A114491 _Don Knuth_, Aug 17 2008, Oct 14 2008