A000027 - OEIS

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A000027 as a triangular array

												1
											2		3
										4		5		6
									7		8		9		10
								11		12		13		14		15
							16		17		18		19		20		21
						22		23		24		25		26		27		28
					29		30		31		32		33		34		35		36
				37		38		39		40		41		42		43		44		45
			46		47		48		49		50		51		52		53		54		55
		56		57		58		59		60		61		62		63		64		65		66
	67		68		69		70		71		72		73		74		75		76		77

A000027 as a square array

1	2	4	7	11	16	22	29	37	46	56	67
3	5	8	12	17	23	30	38	47	57	68
6	9	13	18	24	31	39	48	58	69
10	14	19	25	32	40	49	59	70
15	20	26	33	41	50	60	71
21	27	34	42	51	61	72
28	35	43	52	62	73
36	44	53	63	74
45	54	64	75
55	65	76
66	77

A000027 as an upper right triangle

1	2	4	7	11	16	22	29	37	46	56	67
	3	5	8	12	17	23	30	38	47	57	68
		6	9	13	18	24	31	39	48	58	69
			10	14	19	25	32	40	49	59	70
				15	20	26	33	41	50	60	71
					21	27	34	42	51	61	72
						28	35	43	52	62	73
							36	44	53	63	74
								45	54	64	75
									55	65	76
										66	77