%I #31 Jul 22 2012 17:22:03
%S 1,3,4,7,8,10,14,16,19,20,25,29,32,34,35,41,46,50,53,55,56,63,68,71,
%T 77,81,82,84,92
%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 A213363 at a(12).
%F a(n) = A212124(n)/2.
%e Example 1: written as a triangle in which row i is related to the (i-1)st level of nucleus. Triangle begins:
%e 1;
%e 3, 4;
%e 7, 8, 10;
%e 14, 16, 19, 20;
%e 25, 29, 32, 34, 35;
%e 41, 46, 50, 53, 55, 56;
%e 63, 68, 71, 77, 81, 82, 84;
%e ...
%e Example 2: written as an irregular triangle in which row j is related to the j-th shell of nucleus. Note that in this case row 4 has only one term. Triangle begins:
%e 1;
%e 3, 4;
%e 7, 8, 10;
%e 14,
%e 16, 19, 20, 25;
%e 29, 32, 34, 35, 41;
%e 46, 50, 53, 55, 56, 63;
%e 68, 71, 77, 81, 82, 84, 92;
%e ...
%Y Partial sums of A212121. Other versions are A210983, A212013, A213363, A213373.
%Y Cf. A000292, A004006, A212122, A212124.
%K nonn,tabf,hard,more
%O 1,2
%A _Omar E. Pol_, Jun 03 2012