A064417 - cp's OEIS frontend

A064417 a(1) = 1, a(2) = 2, a(3) = 3; for n >3 a(n) = smallest number not already used such that gcd(a(n), a(n-1)) >= 3.

n	a(n)
1	1
2	2
3	3
4	6
5	9
6	12
7	4
8	8
9	16
10	20
11	5
12	10
13	15
14	18
15	21
16	7
17	14
18	28
19	24
20	27
21	30
22	25
23	35
24	40
25	32
26	36
27	33
28	11
29	22
30	44
31	48
32	39
33	13
34	26
35	52
36	56
37	42
38	45
39	50
40	55
41	60
42	51
43	17
44	34
45	68
46	64
47	72
48	54
49	57
50	19
51	38
52	76
53	80
54	65
55	70
56	49
57	63
58	66
59	69
60	23
61	46
62	92
63	84
64	75
65	78
66	81
67	87
68	29
69	58
70	116
71	88
72	77
73	91

[1, 2, 3, 6, 9, 12, 4, 8, 16, 20, 5, 10, 15, 18, 21, 7, 14, 28, 24, 27, 30, 25, 35, 40, 32, 36, 33, 11, 22, 44, 48, 39, 13, 26, 52, 56, 42, 45, 50, 55, 60, 51, 17, 34, 68, 64, 72, 54, 57, 19, 38, 76, 80, 65, 70, 49, 63, 66, 69, 23, 46, 92, 84, 75, 78, 81, 87, 29, 58, 116, 88, 77, 91]

cp's OEIS Frontend

A064417 a(1) = 1, a(2) = 2, a(3) = 3; for n >3 a(n) = smallest number not already used such that gcd(a(n), a(n-1)) >= 3.

Table of values

List of values

n	a(n)
1	1
2	2
3	3
4	6
5	9
6	12
7	4
8	8
9	16
10	20
11	5
12	10
13	15
14	18
15	21
16	7
17	14
18	28
19	24
20	27
21	30
22	25
23	35
24	40
25	32
26	36
27	33
28	11
29	22
30	44
31	48
32	39
33	13
34	26
35	52
36	56
37	42
38	45
39	50
40	55
41	60
42	51
43	17
44	34
45	68
46	64
47	72
48	54
49	57
50	19
51	38
52	76
53	80
54	65
55	70
56	49
57	63
58	66
59	69
60	23
61	46
62	92
63	84
64	75
65	78
66	81
67	87
68	29
69	58
70	116
71	88
72	77
73	91

n	a(n)
1	1
2	2
3	3
4	6
5	9
6	12
7	4
8	8
9	16
10	20
11	5
12	10
13	15
14	18
15	21
16	7
17	14
18	28
19	24
20	27
21	30
22	25
23	35
24	40
25	32
26	36
27	33
28	11
29	22
30	44
31	48
32	39
33	13
34	26
35	52
36	56
37	42
38	45
39	50
40	55
41	60
42	51
43	17
44	34
45	68
46	64
47	72
48	54
49	57
50	19
51	38
52	76
53	80
54	65
55	70
56	49
57	63
58	66
59	69
60	23
61	46
62	92
63	84
64	75
65	78
66	81
67	87
68	29
69	58
70	116
71	88
72	77
73	91

n	a(n)
1	1
2	2
3	3
4	6
5	9
6	12
7	4
8	8
9	16
10	20
11	5
12	10
13	15
14	18
15	21
16	7
17	14
18	28
19	24
20	27
21	30
22	25
23	35
24	40
25	32
26	36
27	33
28	11
29	22
30	44
31	48
32	39
33	13
34	26
35	52
36	56
37	42
38	45
39	50
40	55
41	60
42	51
43	17
44	34
45	68
46	64
47	72
48	54
49	57
50	19
51	38
52	76
53	80
54	65
55	70
56	49
57	63
58	66
59	69
60	23
61	46
62	92
63	84
64	75
65	78
66	81
67	87
68	29
69	58
70	116
71	88
72	77
73	91