A280985 - cp's OEIS frontend

A280985 a(1)=1, and then a(n) = smallest positive integer not occurring earlier in the sequence sharing some prime factor with at least one of a(n-1) and a(n+1).

n	a(n)
1	1
2	2
3	4
4	3
5	6
6	5
7	10
8	7
9	14
10	8
11	9
12	12
13	11
14	22
15	13
16	26
17	15
18	18
19	16
20	17
21	34
22	19
23	38
24	20
25	21
26	24
27	23
28	46
29	25
30	30
31	27
32	28
33	32
34	29
35	58
36	31
37	62
38	33
39	36
40	35
41	40
42	37
43	74
44	39
45	42
46	41
47	82
48	43
49	86
50	44
51	45
52	48
53	47
54	94
55	49
56	56
57	50
58	51
59	54
60	52
61	53
62	106
63	55
64	60
65	57
66	59
67	118

[1, 2, 4, 3, 6, 5, 10, 7, 14, 8, 9, 12, 11, 22, 13, 26, 15, 18, 16, 17, 34, 19, 38, 20, 21, 24, 23, 46, 25, 30, 27, 28, 32, 29, 58, 31, 62, 33, 36, 35, 40, 37, 74, 39, 42, 41, 82, 43, 86, 44, 45, 48, 47, 94, 49, 56, 50, 51, 54, 52, 53, 106, 55, 60, 57, 59, 118]

cp's OEIS Frontend

A280985 a(1)=1, and then a(n) = smallest positive integer not occurring earlier in the sequence sharing some prime factor with at least one of a(n-1) and a(n+1).

Table of values

List of values

n	a(n)
1	1
2	2
3	4
4	3
5	6
6	5
7	10
8	7
9	14
10	8
11	9
12	12
13	11
14	22
15	13
16	26
17	15
18	18
19	16
20	17
21	34
22	19
23	38
24	20
25	21
26	24
27	23
28	46
29	25
30	30
31	27
32	28
33	32
34	29
35	58
36	31
37	62
38	33
39	36
40	35
41	40
42	37
43	74
44	39
45	42
46	41
47	82
48	43
49	86
50	44
51	45
52	48
53	47
54	94
55	49
56	56
57	50
58	51
59	54
60	52
61	53
62	106
63	55
64	60
65	57
66	59
67	118

n	a(n)
1	1
2	2
3	4
4	3
5	6
6	5
7	10
8	7
9	14
10	8
11	9
12	12
13	11
14	22
15	13
16	26
17	15
18	18
19	16
20	17
21	34
22	19
23	38
24	20
25	21
26	24
27	23
28	46
29	25
30	30
31	27
32	28
33	32
34	29
35	58
36	31
37	62
38	33
39	36
40	35
41	40
42	37
43	74
44	39
45	42
46	41
47	82
48	43
49	86
50	44
51	45
52	48
53	47
54	94
55	49
56	56
57	50
58	51
59	54
60	52
61	53
62	106
63	55
64	60
65	57
66	59
67	118

n	a(n)
1	1
2	2
3	4
4	3
5	6
6	5
7	10
8	7
9	14
10	8
11	9
12	12
13	11
14	22
15	13
16	26
17	15
18	18
19	16
20	17
21	34
22	19
23	38
24	20
25	21
26	24
27	23
28	46
29	25
30	30
31	27
32	28
33	32
34	29
35	58
36	31
37	62
38	33
39	36
40	35
41	40
42	37
43	74
44	39
45	42
46	41
47	82
48	43
49	86
50	44
51	45
52	48
53	47
54	94
55	49
56	56
57	50
58	51
59	54
60	52
61	53
62	106
63	55
64	60
65	57
66	59
67	118