A374739 - cp's OEIS frontend

A374739 a(1) = 1, a(2) = 4; for n > 2, a(n) is the smallest unused positive number that shares a factor with a(n-1) while a(n)/gcd(a(n),a(n-1)) does not equal any previous term.

n	a(n)
1	1
2	4
3	6
4	9
5	15
6	10
7	14
8	16
9	12
10	8
11	20
12	22
13	26
14	34
15	36
16	21
17	33
18	39
19	51
20	54
21	30
22	18
23	27
24	45
25	25
26	35
27	49
28	77
29	55
30	65
31	85
32	95
33	38
34	46
35	48
36	28
37	42
38	57
39	69
40	72
41	40
42	24
43	44
44	52
45	58
46	62
47	64
48	56
49	68
50	74
51	82
52	86
53	94
54	100
55	60
56	50
57	70
58	91
59	119
60	133
61	161
62	115
63	145
64	87
65	93
66	96
67	66
68	78
69	102
70	106
71	118
72	122
73	126

[1, 4, 6, 9, 15, 10, 14, 16, 12, 8, 20, 22, 26, 34, 36, 21, 33, 39, 51, 54, 30, 18, 27, 45, 25, 35, 49, 77, 55, 65, 85, 95, 38, 46, 48, 28, 42, 57, 69, 72, 40, 24, 44, 52, 58, 62, 64, 56, 68, 74, 82, 86, 94, 100, 60, 50, 70, 91, 119, 133, 161, 115, 145, 87, 93, 96, 66, 78, 102, 106, 118, 122, 126]

cp's OEIS Frontend

A374739 a(1) = 1, a(2) = 4; for n > 2, a(n) is the smallest unused positive number that shares a factor with a(n-1) while a(n)/gcd(a(n),a(n-1)) does not equal any previous term.

Table of values

List of values

n	a(n)
1	1
2	4
3	6
4	9
5	15
6	10
7	14
8	16
9	12
10	8
11	20
12	22
13	26
14	34
15	36
16	21
17	33
18	39
19	51
20	54
21	30
22	18
23	27
24	45
25	25
26	35
27	49
28	77
29	55
30	65
31	85
32	95
33	38
34	46
35	48
36	28
37	42
38	57
39	69
40	72
41	40
42	24
43	44
44	52
45	58
46	62
47	64
48	56
49	68
50	74
51	82
52	86
53	94
54	100
55	60
56	50
57	70
58	91
59	119
60	133
61	161
62	115
63	145
64	87
65	93
66	96
67	66
68	78
69	102
70	106
71	118
72	122
73	126

n	a(n)
1	1
2	4
3	6
4	9
5	15
6	10
7	14
8	16
9	12
10	8
11	20
12	22
13	26
14	34
15	36
16	21
17	33
18	39
19	51
20	54
21	30
22	18
23	27
24	45
25	25
26	35
27	49
28	77
29	55
30	65
31	85
32	95
33	38
34	46
35	48
36	28
37	42
38	57
39	69
40	72
41	40
42	24
43	44
44	52
45	58
46	62
47	64
48	56
49	68
50	74
51	82
52	86
53	94
54	100
55	60
56	50
57	70
58	91
59	119
60	133
61	161
62	115
63	145
64	87
65	93
66	96
67	66
68	78
69	102
70	106
71	118
72	122
73	126

n	a(n)
1	1
2	4
3	6
4	9
5	15
6	10
7	14
8	16
9	12
10	8
11	20
12	22
13	26
14	34
15	36
16	21
17	33
18	39
19	51
20	54
21	30
22	18
23	27
24	45
25	25
26	35
27	49
28	77
29	55
30	65
31	85
32	95
33	38
34	46
35	48
36	28
37	42
38	57
39	69
40	72
41	40
42	24
43	44
44	52
45	58
46	62
47	64
48	56
49	68
50	74
51	82
52	86
53	94
54	100
55	60
56	50
57	70
58	91
59	119
60	133
61	161
62	115
63	145
64	87
65	93
66	96
67	66
68	78
69	102
70	106
71	118
72	122
73	126