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 A212319 #20 Oct 27 2013 04:54:15 %S A212319 1,1,2,5,7,13,26,82,104,212,441,1171,1780 %N A212319 The number of abstract groups with minimal permutation representations of degree n. %C A212319 a(n) can be derived by setting a(1)=1 and then taking the differences between the consecutive elements of A174511. This is due to the fact that if an abstract group can be represented as a permutation group on n points, then it can also be represented by a permutation group of degree n+1, simply by including a fixed point. In other words, the sum of the first n terms give you the number of isomorphism classes of subgroups of the symmetric group of degree n. %F A212319 a(1)=1, a(n) = A174511(n) - A174511(n-1), n>1. %e A212319 a(1)=1, since only the trivial group 1 can be represented as permutations of a single point. a(2)=1 because Z_2,1 can both be realized by permutations of two points but for 1 this representation is not minimal. a(3)=2 with Z_3 and S_3 appearing for the first time. %Y A212319 Cf. A174511. %K A212319 nonn,more %O A212319 1,3 %A A212319 _Attila Egri-Nagy_, Oct 25 2013