A340807 - cp's OEIS frontend

A340807 a(n) = n if n <= 3; for n > 3, a(n) is the closest number to a(n-2) that has not occurred earlier and has at least one common factor with a(n-2), but none with a(n-1). In case of a tie, choose the smaller.

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	8
7	15
8	14
9	5
10	12
11	25
12	16
13	35
14	18
15	49
16	20
17	63
18	22
19	57
20	26
21	51
22	28
23	45
24	32
25	39
26	34
27	33
28	38
29	27
30	40
31	21
32	44
33	7
34	46
35	77
36	48
37	91
38	50
39	117
40	55
41	114
42	65
43	112
44	75
45	116
46	69
47	118
48	81
49	122
50	87
51	124
52	99
53	128
54	93
55	130
56	111
57	134
58	105
59	136
60	95
61	138
62	85
63	141
64	80
65	147
66	82
67	153
68	86
69	159
70	88

[1, 2, 3, 4, 9, 8, 15, 14, 5, 12, 25, 16, 35, 18, 49, 20, 63, 22, 57, 26, 51, 28, 45, 32, 39, 34, 33, 38, 27, 40, 21, 44, 7, 46, 77, 48, 91, 50, 117, 55, 114, 65, 112, 75, 116, 69, 118, 81, 122, 87, 124, 99, 128, 93, 130, 111, 134, 105, 136, 95, 138, 85, 141, 80, 147, 82, 153, 86, 159, 88]

cp's OEIS Frontend

A340807 a(n) = n if n <= 3; for n > 3, a(n) is the closest number to a(n-2) that has not occurred earlier and has at least one common factor with a(n-2), but none with a(n-1). In case of a tie, choose the smaller.

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	12
11	25
12	16
13	35
14	18
15	49
16	20
17	63
18	22
19	57
20	26
21	51
22	28
23	45
24	32
25	39
26	34
27	33
28	38
29	27
30	40
31	21
32	44
33	7
34	46
35	77
36	48
37	91
38	50
39	117
40	55
41	114
42	65
43	112
44	75
45	116
46	69
47	118
48	81
49	122
50	87
51	124
52	99
53	128
54	93
55	130
56	111
57	134
58	105
59	136
60	95
61	138
62	85
63	141
64	80
65	147
66	82
67	153
68	86
69	159
70	88

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	8
7	15
8	14
9	5
10	12
11	25
12	16
13	35
14	18
15	49
16	20
17	63
18	22
19	57
20	26
21	51
22	28
23	45
24	32
25	39
26	34
27	33
28	38
29	27
30	40
31	21
32	44
33	7
34	46
35	77
36	48
37	91
38	50
39	117
40	55
41	114
42	65
43	112
44	75
45	116
46	69
47	118
48	81
49	122
50	87
51	124
52	99
53	128
54	93
55	130
56	111
57	134
58	105
59	136
60	95
61	138
62	85
63	141
64	80
65	147
66	82
67	153
68	86
69	159
70	88

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	8
7	15
8	14
9	5
10	12
11	25
12	16
13	35
14	18
15	49
16	20
17	63
18	22
19	57
20	26
21	51
22	28
23	45
24	32
25	39
26	34
27	33
28	38
29	27
30	40
31	21
32	44
33	7
34	46
35	77
36	48
37	91
38	50
39	117
40	55
41	114
42	65
43	112
44	75
45	116
46	69
47	118
48	81
49	122
50	87
51	124
52	99
53	128
54	93
55	130
56	111
57	134
58	105
59	136
60	95
61	138
62	85
63	141
64	80
65	147
66	82
67	153
68	86
69	159
70	88