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 A121942 #4 Mar 27 2019 12:05:00 %S A121942 1,5,22,161,1406,14241,164461,2115335,29903139,460066726,7644586673, %T A121942 136336779596,2596190669230,52552267768902,1126421027176730 %N A121942 Number of digraphs of hydrogen bonded water clusters. %D A121942 T. Miyake and M. Aida, "Enumeration of topology-distinct structures of hydrogen bonded water clusters", Chem. Phys. Lett., vol. 363 (2002) pp. 106-110. See Table 1 column 3 on page 109. %H A121942 B. Brinkmann, <a href="https://doi.org/10.1007/s10910-008-9496-y">Generating water clusters and other directed graphs</a>, J. Math. Chem. 46 (4) (2009) 1112-1121, Table 1. %e A121942 If n=5 then the number of digraphs of hydrogen bonded water clusters is 161. %K A121942 nonn %O A121942 2,2 %A A121942 _Parthasarathy Nambi_, Sep 03 2006 %E A121942 More terms copied from Brinkmann's table. - _R. J. Mathar_, Mar 27 2019