A213371 Triangle read by rows in which row n lists the number of pairs of states of the subshells of the n-th shell of the nuclear shell model ordered by energy level in increasing order.

1, 2, 1, 3, 1, 2, 4, 2, 3, 1, 5, 4, 3, 6, 2, 1, 4, 5, 7, 2, 3, 1

Offset: 1

Author

Omar E. Pol, Jul 16 2012

Keywords

• nonn
• tabf
• hard
• more

Comments

First differs from A212121 at a(14). The illustration of initial terms is essentially the same as the illustration of initial terms of A213372, the main entry for this sequence.

Examples

			Written as an irregular triangle in which row n represents the n-th shell of nucleus. Note that row 4 has only one term. Triangle begins:
1;
2, 1;
3, 1, 2;
4;
2, 3, 1, 5;
4, 3, 6, 2, 1;
4, 5, 7, 2, 3, 1;
		

Links

• MIT OpenCourseWare, Energy Levels of Nucleons in a Smoothly-Varying Potential Well

Crossrefs

Partial sums give A213373. Other version are A004736, A130517, A212121, A213361.

Cf. A213372, A213374.

Formula

a(n) = A213372(n)/2.