A375563 - cp's OEIS frontend

A375563 a(1) = 1; for n > 1, a(n) is the smallest unused positive number that shares a factor with a(n-1) if a(n-1) is prime, otherwise a(n) is coprime to 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	9
11	8
12	11
13	22
14	13
15	26
16	15
17	16
18	17
19	34
20	19
21	38
22	21
23	20
24	23
25	46
26	25
27	12
28	29
29	58
30	27
31	28
32	31
33	62
34	33
35	32
36	35
37	18
38	37
39	74
40	39
41	40
42	41
43	82
44	43
45	86
46	45
47	44
48	47
49	94
50	49
51	24
52	53
53	106
54	51
55	50
56	57
57	52
58	55
59	36
60	59
61	118
62	61
63	122
64	63
65	64
66	65
67	42
68	67
69	134
70	69
71	56
72	71
73	142
74	73
75	146

[1, 2, 4, 3, 6, 5, 10, 7, 14, 9, 8, 11, 22, 13, 26, 15, 16, 17, 34, 19, 38, 21, 20, 23, 46, 25, 12, 29, 58, 27, 28, 31, 62, 33, 32, 35, 18, 37, 74, 39, 40, 41, 82, 43, 86, 45, 44, 47, 94, 49, 24, 53, 106, 51, 50, 57, 52, 55, 36, 59, 118, 61, 122, 63, 64, 65, 42, 67, 134, 69, 56, 71, 142, 73, 146]

cp's OEIS Frontend

A375563 a(1) = 1; for n > 1, a(n) is the smallest unused positive number that shares a factor with a(n-1) if a(n-1) is prime, otherwise a(n) is coprime to 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	9
11	8
12	11
13	22
14	13
15	26
16	15
17	16
18	17
19	34
20	19
21	38
22	21
23	20
24	23
25	46
26	25
27	12
28	29
29	58
30	27
31	28
32	31
33	62
34	33
35	32
36	35
37	18
38	37
39	74
40	39
41	40
42	41
43	82
44	43
45	86
46	45
47	44
48	47
49	94
50	49
51	24
52	53
53	106
54	51
55	50
56	57
57	52
58	55
59	36
60	59
61	118
62	61
63	122
64	63
65	64
66	65
67	42
68	67
69	134
70	69
71	56
72	71
73	142
74	73
75	146

n	a(n)
1	1
2	2
3	4
4	3
5	6
6	5
7	10
8	7
9	14
10	9
11	8
12	11
13	22
14	13
15	26
16	15
17	16
18	17
19	34
20	19
21	38
22	21
23	20
24	23
25	46
26	25
27	12
28	29
29	58
30	27
31	28
32	31
33	62
34	33
35	32
36	35
37	18
38	37
39	74
40	39
41	40
42	41
43	82
44	43
45	86
46	45
47	44
48	47
49	94
50	49
51	24
52	53
53	106
54	51
55	50
56	57
57	52
58	55
59	36
60	59
61	118
62	61
63	122
64	63
65	64
66	65
67	42
68	67
69	134
70	69
71	56
72	71
73	142
74	73
75	146

n	a(n)
1	1
2	2
3	4
4	3
5	6
6	5
7	10
8	7
9	14
10	9
11	8
12	11
13	22
14	13
15	26
16	15
17	16
18	17
19	34
20	19
21	38
22	21
23	20
24	23
25	46
26	25
27	12
28	29
29	58
30	27
31	28
32	31
33	62
34	33
35	32
36	35
37	18
38	37
39	74
40	39
41	40
42	41
43	82
44	43
45	86
46	45
47	44
48	47
49	94
50	49
51	24
52	53
53	106
54	51
55	50
56	57
57	52
58	55
59	36
60	59
61	118
62	61
63	122
64	63
65	64
66	65
67	42
68	67
69	134
70	69
71	56
72	71
73	142
74	73
75	146