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%I #20 Jul 21 2012 12:37:07
%S 1,3,4,7,8,10,14,16,19,20,25,28,32,33,35,41,45,47,54,59,60,63,68,74,
%T 82,85,86,90,92
%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 A212123 at a(12).
%F a(n) = A213364(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 1;
%e 3, 4;
%e 7, 8, 10;
%e 14;
%e 16, 19, 20, 25;
%e 28, 32, 33, 35, 41;
%e 45, 47, 54, 59, 60, 63;
%e 68, 74, 82, 85, 86, 90, 92;
%e ...
%Y Partial sums of A213361. Other versions are A210983, A212013, A213373.
%Y Cf. A018226, A212121-A212124, A213362, A213364.
%K nonn,tabf,hard,more
%O 1,2
%A _Omar E. Pol_, Jun 23 2012