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 A184944 #23 May 01 2014 02:36:24
%S A184944 0,0,0,0,0,0,0,0,1,0,2,2,12,31,220,1606,16828,193900,2452818,32670329,
%T A184944 456028472,6636066091,100135577616,1582718909051
%N A184944 Number of connected 4-regular simple graphs on n vertices with girth exactly 4.
%H A184944 Jason Kimberley, <a href="/wiki/User:Jason_Kimberley/C_k-reg_girth_eq_g_index">Index of sequences counting connected k-regular simple graphs with girth exactly g</a>
%F A184944 a(n) = A033886(n) - A058343(n).
%e A184944 a(0)=0 because even though the null graph (on zero vertices) is vacuously 4-regular and connected, since it is acyclic, it has infinite girth.
%e A184944 The a(8)=1 graph is the complete bipartite graph K_{4,4}.
%Y A184944 4-regular simple graphs with girth exactly 4: this sequence (connected), A185044 (disconnected), A185144 (not necessarily connected).
%Y A184944 Connected k-regular simple graphs with girth exactly 4: A006924 (k=3), this sequence (k=4), A184954 (k=5), A184964 (k=6), A184974 (k=7).
%Y A184944 Connected 4-regular simple graphs with girth at least g: A006820 (g=3), A033886 (g=4), A058343 (g=5), A058348 (g=6).
%Y A184944 Connected 4-regular simple graphs with girth exactly g: A184943 (g=3), this sequence (g=4), A184945 (g=5).
%K A184944 nonn,hard,more
%O A184944 0,11
%A A184944 _Jason Kimberley_, Jan 26 2011
%E A184944 a(23) was appended by the author once A033886(23) was known, Nov 03 2011