A377157 - cp's OEIS frontend

A377157 a(n) = n for n <= 3; for n > 3, a(n) is the smallest unused positive number that is coprime to a(n-1) if a(n-1) is prime and coprime to a(n-2) if a(n-2) is prime, else a(n) shares a factor with a(n-1) and a(n-2) if both are composite.

n	a(n)
1	1
2	2
3	3
4	5
5	4
6	6
7	8
8	10
9	12
10	14
11	16
12	18
13	20
14	15
15	24
16	9
17	21
18	27
19	30
20	33
21	22
22	11
23	7
24	13
25	17
26	19
27	23
28	25
29	26
30	40
31	28
32	32
33	34
34	36
35	38
36	42
37	44
38	46
39	48
40	50
41	45
42	35
43	55
44	60
45	65
46	39
47	52
48	54
49	56
50	58
51	62
52	64
53	66
54	68
55	51
56	72
57	57
58	63
59	69
60	75
61	78
62	70
63	74
64	76
65	80
66	82
67	84
68	86
69	88
70	90
71	92
72	94
73	96
74	98
75	100
76	102
77	85
78	105
79	95
80	110
81	114
82	99
83	81
84	87
85	93
86	108
87	111
88	117
89	120
90	104

[1, 2, 3, 5, 4, 6, 8, 10, 12, 14, 16, 18, 20, 15, 24, 9, 21, 27, 30, 33, 22, 11, 7, 13, 17, 19, 23, 25, 26, 40, 28, 32, 34, 36, 38, 42, 44, 46, 48, 50, 45, 35, 55, 60, 65, 39, 52, 54, 56, 58, 62, 64, 66, 68, 51, 72, 57, 63, 69, 75, 78, 70, 74, 76, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 85, 105, 95, 110, 114, 99, 81, 87, 93, 108, 111, 117, 120, 104]

cp's OEIS Frontend

A377157 a(n) = n for n <= 3; for n > 3, a(n) is the smallest unused positive number that is coprime to a(n-1) if a(n-1) is prime and coprime to a(n-2) if a(n-2) is prime, else a(n) shares a factor with a(n-1) and a(n-2) if both are composite.

Table of values

List of values

n	a(n)
1	1
2	2
3	3
4	5
5	4
6	6
7	8
8	10
9	12
10	14
11	16
12	18
13	20
14	15
15	24
16	9
17	21
18	27
19	30
20	33
21	22
22	11
23	7
24	13
25	17
26	19
27	23
28	25
29	26
30	40
31	28
32	32
33	34
34	36
35	38
36	42
37	44
38	46
39	48
40	50
41	45
42	35
43	55
44	60
45	65
46	39
47	52
48	54
49	56
50	58
51	62
52	64
53	66
54	68
55	51
56	72
57	57
58	63
59	69
60	75
61	78
62	70
63	74
64	76
65	80
66	82
67	84
68	86
69	88
70	90
71	92
72	94
73	96
74	98
75	100
76	102
77	85
78	105
79	95
80	110
81	114
82	99
83	81
84	87
85	93
86	108
87	111
88	117
89	120
90	104

n	a(n)
1	1
2	2
3	3
4	5
5	4
6	6
7	8
8	10
9	12
10	14
11	16
12	18
13	20
14	15
15	24
16	9
17	21
18	27
19	30
20	33
21	22
22	11
23	7
24	13
25	17
26	19
27	23
28	25
29	26
30	40
31	28
32	32
33	34
34	36
35	38
36	42
37	44
38	46
39	48
40	50
41	45
42	35
43	55
44	60
45	65
46	39
47	52
48	54
49	56
50	58
51	62
52	64
53	66
54	68
55	51
56	72
57	57
58	63
59	69
60	75
61	78
62	70
63	74
64	76
65	80
66	82
67	84
68	86
69	88
70	90
71	92
72	94
73	96
74	98
75	100
76	102
77	85
78	105
79	95
80	110
81	114
82	99
83	81
84	87
85	93
86	108
87	111
88	117
89	120
90	104

n	a(n)
1	1
2	2
3	3
4	5
5	4
6	6
7	8
8	10
9	12
10	14
11	16
12	18
13	20
14	15
15	24
16	9
17	21
18	27
19	30
20	33
21	22
22	11
23	7
24	13
25	17
26	19
27	23
28	25
29	26
30	40
31	28
32	32
33	34
34	36
35	38
36	42
37	44
38	46
39	48
40	50
41	45
42	35
43	55
44	60
45	65
46	39
47	52
48	54
49	56
50	58
51	62
52	64
53	66
54	68
55	51
56	72
57	57
58	63
59	69
60	75
61	78
62	70
63	74
64	76
65	80
66	82
67	84
68	86
69	88
70	90
71	92
72	94
73	96
74	98
75	100
76	102
77	85
78	105
79	95
80	110
81	114
82	99
83	81
84	87
85	93
86	108
87	111
88	117
89	120
90	104