A373902 - cp's OEIS frontend

A373902 a(1) = 2; for n > 1, a(n) is the smallest positive number that does not equal a(n-1), shares a factor with a(n-1), and has not appeared as an adjacent term to a(n-1) previously in the sequence.

n	a(n)
1	2
2	4
3	6
4	2
5	8
6	4
7	10
8	2
9	12
10	3
11	6
12	8
13	10
14	5
15	15
16	3
17	9
18	6
19	10
20	12
21	4
22	14
23	2
24	16
25	4
26	18
27	2
28	20
29	4
30	22
31	2
32	24
33	3
34	18
35	6
36	12
37	8
38	14
39	6
40	15
41	9
42	12
43	14
44	7
45	21
46	3
47	27
48	6
49	16
50	8
51	18
52	9
53	21
54	6
55	20
56	5
57	25
58	10
59	14
60	16
61	10
62	15
63	12
64	16
65	18
66	10
67	20
68	8
69	22
70	6
71	24
72	4
73	26
74	2
75	28
76	4
77	30
78	2
79	32
80	4
81	34
82	2
83	36
84	3

[2, 4, 6, 2, 8, 4, 10, 2, 12, 3, 6, 8, 10, 5, 15, 3, 9, 6, 10, 12, 4, 14, 2, 16, 4, 18, 2, 20, 4, 22, 2, 24, 3, 18, 6, 12, 8, 14, 6, 15, 9, 12, 14, 7, 21, 3, 27, 6, 16, 8, 18, 9, 21, 6, 20, 5, 25, 10, 14, 16, 10, 15, 12, 16, 18, 10, 20, 8, 22, 6, 24, 4, 26, 2, 28, 4, 30, 2, 32, 4, 34, 2, 36, 3]

cp's OEIS Frontend

A373902 a(1) = 2; for n > 1, a(n) is the smallest positive number that does not equal a(n-1), shares a factor with a(n-1), and has not appeared as an adjacent term to a(n-1) previously in the sequence.

Table of values

List of values

n	a(n)
1	2
2	4
3	6
4	2
5	8
6	4
7	10
8	2
9	12
10	3
11	6
12	8
13	10
14	5
15	15
16	3
17	9
18	6
19	10
20	12
21	4
22	14
23	2
24	16
25	4
26	18
27	2
28	20
29	4
30	22
31	2
32	24
33	3
34	18
35	6
36	12
37	8
38	14
39	6
40	15
41	9
42	12
43	14
44	7
45	21
46	3
47	27
48	6
49	16
50	8
51	18
52	9
53	21
54	6
55	20
56	5
57	25
58	10
59	14
60	16
61	10
62	15
63	12
64	16
65	18
66	10
67	20
68	8
69	22
70	6
71	24
72	4
73	26
74	2
75	28
76	4
77	30
78	2
79	32
80	4
81	34
82	2
83	36
84	3

n	a(n)
1	2
2	4
3	6
4	2
5	8
6	4
7	10
8	2
9	12
10	3
11	6
12	8
13	10
14	5
15	15
16	3
17	9
18	6
19	10
20	12
21	4
22	14
23	2
24	16
25	4
26	18
27	2
28	20
29	4
30	22
31	2
32	24
33	3
34	18
35	6
36	12
37	8
38	14
39	6
40	15
41	9
42	12
43	14
44	7
45	21
46	3
47	27
48	6
49	16
50	8
51	18
52	9
53	21
54	6
55	20
56	5
57	25
58	10
59	14
60	16
61	10
62	15
63	12
64	16
65	18
66	10
67	20
68	8
69	22
70	6
71	24
72	4
73	26
74	2
75	28
76	4
77	30
78	2
79	32
80	4
81	34
82	2
83	36
84	3

n	a(n)
1	2
2	4
3	6
4	2
5	8
6	4
7	10
8	2
9	12
10	3
11	6
12	8
13	10
14	5
15	15
16	3
17	9
18	6
19	10
20	12
21	4
22	14
23	2
24	16
25	4
26	18
27	2
28	20
29	4
30	22
31	2
32	24
33	3
34	18
35	6
36	12
37	8
38	14
39	6
40	15
41	9
42	12
43	14
44	7
45	21
46	3
47	27
48	6
49	16
50	8
51	18
52	9
53	21
54	6
55	20
56	5
57	25
58	10
59	14
60	16
61	10
62	15
63	12
64	16
65	18
66	10
67	20
68	8
69	22
70	6
71	24
72	4
73	26
74	2
75	28
76	4
77	30
78	2
79	32
80	4
81	34
82	2
83	36
84	3