%N 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 First differs from A212123 at a(14). For more information see A213372.
%H 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 a(n) = A213374(n)/2.
%e 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 3, 4;
%e 7, 8, 10;
%e 16, 19, 20, 25;
%e 29, 32, 38, 40, 41;
%e 45, 50, 57, 59, 62, 63;
%Y Partial sums of A213371. Other versions are A210983, A212013, A212123, A213363.
%Y Cf. A018226, A213372, A213374.
%A _Omar E. Pol_, Jul 16 2012