A003991 - OEIS

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A003991 as a triangular array

												1
											2		2
										3		4		3
									4		6		6		4
								5		8		9		8		5
							6		10		12		12		10		6
						7		12		15		16		15		12		7
					8		14		18		20		20		18		14		8
				9		16		21		24		25		24		21		16		9
			10		18		24		28		30		30		28		24		18		10
		11		20		27		32		35		36		35		32		27		20		11
	12		22		30		36		40		42		42		40		36		30		22		12

A003991 as a square array

1	2	3	4	5	6	7	8	9	10	11	12
2	4	6	8	10	12	14	16	18	20	22
3	6	9	12	15	18	21	24	27	30
4	8	12	16	20	24	28	32	36
5	10	15	20	25	30	35	40
6	12	18	24	30	36	42
7	14	21	28	35	42
8	16	24	32	40
9	18	27	36
10	20	30
11	22
12

A003991 as an upper right triangle

1	2	3	4	5	6	7	8	9	10	11	12
	2	4	6	8	10	12	14	16	18	20	22
		3	6	9	12	15	18	21	24	27	30
			4	8	12	16	20	24	28	32	36
				5	10	15	20	25	30	35	40
					6	12	18	24	30	36	42
						7	14	21	28	35	42
							8	16	24	32	40
								9	18	27	36
									10	20	30
										11	22
											12