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 A213373 #13 Sep 03 2012 07:13:16 %S A213373 1,3,4,7,8,10,14,16,19,20,25,29,32,38,40,41,45,50,57,59,62,63 %N A213373 Total number of pairs of states of the first n subshells of the nuclear shell model in which the subshells are ordered by energy level in increasing order. %C A213373 First differs from A212123 at a(14). For more information see A213372. %H A213373 MIT OpenCourseWare, <a href="http://www.flickr.com/photos/mitopencourseware/3772864128/in/set-72157621892931990">Energy Levels of Nucleons in a Smoothly-Varying Potential Well</a> %F A213373 a(n) = A213374(n)/2. %e A213373 Written as an irregular triangle in which row j is related to the j-th shell of nucleus. Note that row 4 has only one term. Triangle begins: %e A213373 1; %e A213373 3, 4; %e A213373 7, 8, 10; %e A213373 14; %e A213373 16, 19, 20, 25; %e A213373 29, 32, 38, 40, 41; %e A213373 45, 50, 57, 59, 62, 63; %e A213373 ... %Y A213373 Partial sums of A213371. Other versions are A210983, A212013, A212123, A213363. %Y A213373 Cf. A018226, A213372, A213374. %K A213373 nonn,tabf,hard,more %O A213373 1,2 %A A213373 _Omar E. Pol_, Jul 16 2012