A098550 - cp's OEIS frontend

A098550 The Yellowstone permutation: a(n) = n if n <= 3, otherwise the smallest number not occurring earlier having at least one common factor with a(n-2), but none with a(n-1).

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	8
7	15
8	14
9	5
10	6
11	25
12	12
13	35
14	16
15	7
16	10
17	21
18	20
19	27
20	22
21	39
22	11
23	13
24	33
25	26
26	45
27	28
28	51
29	32
30	17
31	18
32	85
33	24
34	55
35	34
36	65
37	36
38	91
39	30
40	49
41	38
42	63
43	19
44	42
45	95
46	44
47	57
48	40
49	69
50	50
51	23
52	48
53	115
54	52
55	75
56	46
57	81
58	56
59	87
60	62
61	29
62	31
63	58
64	93
65	64
66	99
67	68
68	77
69	54
70	119
71	60

[1, 2, 3, 4, 9, 8, 15, 14, 5, 6, 25, 12, 35, 16, 7, 10, 21, 20, 27, 22, 39, 11, 13, 33, 26, 45, 28, 51, 32, 17, 18, 85, 24, 55, 34, 65, 36, 91, 30, 49, 38, 63, 19, 42, 95, 44, 57, 40, 69, 50, 23, 48, 115, 52, 75, 46, 81, 56, 87, 62, 29, 31, 58, 93, 64, 99, 68, 77, 54, 119, 60]

cp's OEIS Frontend

A098550 The Yellowstone permutation: a(n) = n if n <= 3, otherwise the smallest number not occurring earlier having at least one common factor with a(n-2), but none with a(n-1).

Table of values

List of values

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	8
7	15
8	14
9	5
10	6
11	25
12	12
13	35
14	16
15	7
16	10
17	21
18	20
19	27
20	22
21	39
22	11
23	13
24	33
25	26
26	45
27	28
28	51
29	32
30	17
31	18
32	85
33	24
34	55
35	34
36	65
37	36
38	91
39	30
40	49
41	38
42	63
43	19
44	42
45	95
46	44
47	57
48	40
49	69
50	50
51	23
52	48
53	115
54	52
55	75
56	46
57	81
58	56
59	87
60	62
61	29
62	31
63	58
64	93
65	64
66	99
67	68
68	77
69	54
70	119
71	60

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	8
7	15
8	14
9	5
10	6
11	25
12	12
13	35
14	16
15	7
16	10
17	21
18	20
19	27
20	22
21	39
22	11
23	13
24	33
25	26
26	45
27	28
28	51
29	32
30	17
31	18
32	85
33	24
34	55
35	34
36	65
37	36
38	91
39	30
40	49
41	38
42	63
43	19
44	42
45	95
46	44
47	57
48	40
49	69
50	50
51	23
52	48
53	115
54	52
55	75
56	46
57	81
58	56
59	87
60	62
61	29
62	31
63	58
64	93
65	64
66	99
67	68
68	77
69	54
70	119
71	60

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	8
7	15
8	14
9	5
10	6
11	25
12	12
13	35
14	16
15	7
16	10
17	21
18	20
19	27
20	22
21	39
22	11
23	13
24	33
25	26
26	45
27	28
28	51
29	32
30	17
31	18
32	85
33	24
34	55
35	34
36	65
37	36
38	91
39	30
40	49
41	38
42	63
43	19
44	42
45	95
46	44
47	57
48	40
49	69
50	50
51	23
52	48
53	115
54	52
55	75
56	46
57	81
58	56
59	87
60	62
61	29
62	31
63	58
64	93
65	64
66	99
67	68
68	77
69	54
70	119
71	60