A026820 - OEIS

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A026820 as a triangular array

												1
											1		2
										1		2		3
									1		3		4		5
								1		3		5		6		7
							1		4		7		9		10		11
						1		4		8		11		13		14		15
					1		5		10		15		18		20		21		22
				1		5		12		18		23		26		28		29		30
			1		6		14		23		30		35		38		40		41		42
		1		6		16		27		37		44		49		52		54		55		56
	1		7		19		34		47		58		65		70		73		75		76		77

A026820 as a square array

1	1	1	1	1	1	1	1	1	1	1	1
2	2	3	3	4	4	5	5	6	6	7
3	4	5	7	8	10	12	14	16	19
5	6	9	11	15	18	23	27	34
7	10	13	18	23	30	37	47
11	14	20	26	35	44	58
15	21	28	38	49	65
22	29	40	52	70
30	41	54	73
42	55	75
56	76
77

A026820 as an upper right triangle

1	1	1	1	1	1	1	1	1	1	1	1
	2	2	3	3	4	4	5	5	6	6	7
		3	4	5	7	8	10	12	14	16	19
			5	6	9	11	15	18	23	27	34
				7	10	13	18	23	30	37	47
					11	14	20	26	35	44	58
						15	21	28	38	49	65
							22	29	40	52	70
								30	41	54	73
									42	55	75
										56	76
											77