A373390 - cp's OEIS frontend

A373390 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 at least one of a(1)...a(n-2).

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

cp's OEIS Frontend

A373390 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 at least one of a(1)...a(n-2).

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	7
12	10
13	21
14	16
15	25
16	12
17	35
18	18
19	49
20	20
21	27
22	22
23	39
24	11
25	13
26	24
27	55
28	26
29	33
30	28
31	45
32	32
33	51
34	38
35	17
36	19
37	30
38	77
39	34
40	57
41	40
42	63
43	44
44	65
45	36
46	85
47	42
48	95
49	46
50	75
51	23
52	48
53	91
54	50
55	69
56	52
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	7
12	10
13	21
14	16
15	25
16	12
17	35
18	18
19	49
20	20
21	27
22	22
23	39
24	11
25	13
26	24
27	55
28	26
29	33
30	28
31	45
32	32
33	51
34	38
35	17
36	19
37	30
38	77
39	34
40	57
41	40
42	63
43	44
44	65
45	36
46	85
47	42
48	95
49	46
50	75
51	23
52	48
53	91
54	50
55	69
56	52
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	7
12	10
13	21
14	16
15	25
16	12
17	35
18	18
19	49
20	20
21	27
22	22
23	39
24	11
25	13
26	24
27	55
28	26
29	33
30	28
31	45
32	32
33	51
34	38
35	17
36	19
37	30
38	77
39	34
40	57
41	40
42	63
43	44
44	65
45	36
46	85
47	42
48	95
49	46
50	75
51	23
52	48
53	91
54	50
55	69
56	52
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