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 A121159 #2 Mar 30 2012 17:25:49 %S A121159 1,4,16,53,175,547,1692,5127,15408,45831,135500,398186,1165005, %T A121159 3394880,9861048,28561403,82525483,237941827,684778523,1967510639 %N A121159 Number of spiro bicyclic skeletons with n carbon atoms (see Parks et al. for precise definition). %D A121159 Camden A. Parks and James B. Hendrickson, Enumeration of monocyclic and bicyclic carbon skeletons, J. Chem. Inf. Comput. Sci., vol. 31, 334-339 (1991). %K A121159 nonn %O A121159 6,2 %A A121159 _Parthasarathy Nambi_, Aug 13 2006