A374612 - cp's OEIS frontend

A374612 a(n) = n for n <= 3; for n > 3, a(n) is the smallest unused positive number that is coprime to a(n-1) but has a common factor with any other previous term that is also coprime to a(n-1).

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	8
7	15
8	14
9	5
10	6
11	25
12	7
13	10
14	21
15	16
16	27
17	20
18	33
19	26
20	11
21	12
22	35
23	13
24	18
25	49
26	22
27	39
28	28
29	45
30	32
31	51
32	38
33	17
34	19
35	24
36	55
37	34
38	57
39	40
40	63
41	44
42	65
43	36
44	77
45	30
46	91
47	46
48	75
49	23
50	42
51	85
52	48
53	95
54	52
55	69
56	50
57	81
58	56
59	87
60	62
61	29
62	31
63	54
64	115
65	58
66	93
67	64
68	99
69	68
70	105
71	74
72	117
73	37
74	60
75	119
76	66

[1, 2, 3, 4, 9, 8, 15, 14, 5, 6, 25, 7, 10, 21, 16, 27, 20, 33, 26, 11, 12, 35, 13, 18, 49, 22, 39, 28, 45, 32, 51, 38, 17, 19, 24, 55, 34, 57, 40, 63, 44, 65, 36, 77, 30, 91, 46, 75, 23, 42, 85, 48, 95, 52, 69, 50, 81, 56, 87, 62, 29, 31, 54, 115, 58, 93, 64, 99, 68, 105, 74, 117, 37, 60, 119, 66]

cp's OEIS Frontend

A374612 a(n) = n for n <= 3; for n > 3, a(n) is the smallest unused positive number that is coprime to a(n-1) but has a common factor with any other previous term that is also coprime to a(n-1).

Table of values

List of values

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	8
7	15
8	14
9	5
10	6
11	25
12	7
13	10
14	21
15	16
16	27
17	20
18	33
19	26
20	11
21	12
22	35
23	13
24	18
25	49
26	22
27	39
28	28
29	45
30	32
31	51
32	38
33	17
34	19
35	24
36	55
37	34
38	57
39	40
40	63
41	44
42	65
43	36
44	77
45	30
46	91
47	46
48	75
49	23
50	42
51	85
52	48
53	95
54	52
55	69
56	50
57	81
58	56
59	87
60	62
61	29
62	31
63	54
64	115
65	58
66	93
67	64
68	99
69	68
70	105
71	74
72	117
73	37
74	60
75	119
76	66

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	8
7	15
8	14
9	5
10	6
11	25
12	7
13	10
14	21
15	16
16	27
17	20
18	33
19	26
20	11
21	12
22	35
23	13
24	18
25	49
26	22
27	39
28	28
29	45
30	32
31	51
32	38
33	17
34	19
35	24
36	55
37	34
38	57
39	40
40	63
41	44
42	65
43	36
44	77
45	30
46	91
47	46
48	75
49	23
50	42
51	85
52	48
53	95
54	52
55	69
56	50
57	81
58	56
59	87
60	62
61	29
62	31
63	54
64	115
65	58
66	93
67	64
68	99
69	68
70	105
71	74
72	117
73	37
74	60
75	119
76	66

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	8
7	15
8	14
9	5
10	6
11	25
12	7
13	10
14	21
15	16
16	27
17	20
18	33
19	26
20	11
21	12
22	35
23	13
24	18
25	49
26	22
27	39
28	28
29	45
30	32
31	51
32	38
33	17
34	19
35	24
36	55
37	34
38	57
39	40
40	63
41	44
42	65
43	36
44	77
45	30
46	91
47	46
48	75
49	23
50	42
51	85
52	48
53	95
54	52
55	69
56	50
57	81
58	56
59	87
60	62
61	29
62	31
63	54
64	115
65	58
66	93
67	64
68	99
69	68
70	105
71	74
72	117
73	37
74	60
75	119
76	66