A138609 - OEIS

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A138609 as a triangular array

												1
											3		4
										2		5		6
									7		8		11		12
								9		10		13		14		17
							15		16		19		20		23		24
						18		21		22		25		26		29		30
					27		28		31		32		35		36		39		40
				33		34		37		38		41		42		45		46		49
			43		44		47		48		51		52		55		56		59		60
		50		53		54		57		58		61		62		65		66		69		70
	63		64		67		68		71		72

A138609 as a square array

1	3	2	7	9	15	18	27	33	43	50	63
4	5	8	10	16	21	28	34	44	53	64
6	11	13	19	22	31	37	47	54	67
12	14	20	25	32	38	48	57	68
17	23	26	35	41	51	58	71
24	29	36	42	52	61	72
30	39	45	55	62
40	46	56	65
49	59	66
60	69
70

A138609 as an upper right triangle

1	3	2	7	9	15	18	27	33	43	50	63
	4	5	8	10	16	21	28	34	44	53	64
		6	11	13	19	22	31	37	47	54	67
			12	14	20	25	32	38	48	57	68
				17	23	26	35	41	51	58	71
					24	29	36	42	52	61	72
						30	39	45	55	62
							40	46	56	65
								49	59	66
									60	69
										70