A120913 - OEIS

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A120913 as a triangular array

												1
											3		2
										6		5		4
									10		8		9		7
								15		13		12		14		11
							21		18		17		19		20		16
						28		25		24		23		26		27		22
					36		32		31		30		33		34		35		29
				45		41		39		40		38		42		43		44		37
			55		50		49		48		47		51		52		53		54		46
		66		61		59		58		60		57		62		63		64		65		56
	78		72		70		69		71		68

A120913 as a square array

1	3	6	10	15	21	28	36	45	55	66	78
2	5	8	13	18	25	32	41	50	61	72
4	9	12	17	24	31	39	49	59	70
7	14	19	23	30	40	48	58	69
11	20	26	33	38	47	60	71
16	27	34	42	51	57	68
22	35	43	52	62
29	44	53	63
37	54	64
46	65
56

A120913 as an upper right triangle

1	3	6	10	15	21	28	36	45	55	66	78
	2	5	8	13	18	25	32	41	50	61	72
		4	9	12	17	24	31	39	49	59	70
			7	14	19	23	30	40	48	58	69
				11	20	26	33	38	47	60	71
					16	27	34	42	51	57	68
						22	35	43	52	62
							29	44	53	63
								37	54	64
									46	65
										56