A340783 - cp's OEIS frontend

A340783 a(n) = n if n <= 3; for n>3, a(n) = the closest number to a(n-1) 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	6
11	25
12	24
13	35
14	34
15	45
16	44
17	39
18	38
19	33
20	32
21	27
22	26
23	21
24	20
25	7
26	10
27	49
28	48
29	77
30	76
31	63
32	62
33	57
34	56
35	51
36	50
37	69
38	68
39	75
40	74
41	81
42	80
43	87
44	86
45	93
46	92
47	99
48	98
49	111
50	110
51	117
52	116
53	123
54	122
55	129
56	128
57	135
58	134
59	141
60	140
61	153
62	152
63	147
64	146
65	133
66	132
67	119
68	118
69	105
70	104
71	95

[1, 2, 3, 4, 9, 8, 15, 14, 5, 6, 25, 24, 35, 34, 45, 44, 39, 38, 33, 32, 27, 26, 21, 20, 7, 10, 49, 48, 77, 76, 63, 62, 57, 56, 51, 50, 69, 68, 75, 74, 81, 80, 87, 86, 93, 92, 99, 98, 111, 110, 117, 116, 123, 122, 129, 128, 135, 134, 141, 140, 153, 152, 147, 146, 133, 132, 119, 118, 105, 104, 95]

cp's OEIS Frontend

A340783 a(n) = n if n <= 3; for n>3, a(n) = the closest number to a(n-1) 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	6
11	25
12	24
13	35
14	34
15	45
16	44
17	39
18	38
19	33
20	32
21	27
22	26
23	21
24	20
25	7
26	10
27	49
28	48
29	77
30	76
31	63
32	62
33	57
34	56
35	51
36	50
37	69
38	68
39	75
40	74
41	81
42	80
43	87
44	86
45	93
46	92
47	99
48	98
49	111
50	110
51	117
52	116
53	123
54	122
55	129
56	128
57	135
58	134
59	141
60	140
61	153
62	152
63	147
64	146
65	133
66	132
67	119
68	118
69	105
70	104
71	95

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	24
13	35
14	34
15	45
16	44
17	39
18	38
19	33
20	32
21	27
22	26
23	21
24	20
25	7
26	10
27	49
28	48
29	77
30	76
31	63
32	62
33	57
34	56
35	51
36	50
37	69
38	68
39	75
40	74
41	81
42	80
43	87
44	86
45	93
46	92
47	99
48	98
49	111
50	110
51	117
52	116
53	123
54	122
55	129
56	128
57	135
58	134
59	141
60	140
61	153
62	152
63	147
64	146
65	133
66	132
67	119
68	118
69	105
70	104
71	95

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	24
13	35
14	34
15	45
16	44
17	39
18	38
19	33
20	32
21	27
22	26
23	21
24	20
25	7
26	10
27	49
28	48
29	77
30	76
31	63
32	62
33	57
34	56
35	51
36	50
37	69
38	68
39	75
40	74
41	81
42	80
43	87
44	86
45	93
46	92
47	99
48	98
49	111
50	110
51	117
52	116
53	123
54	122
55	129
56	128
57	135
58	134
59	141
60	140
61	153
62	152
63	147
64	146
65	133
66	132
67	119
68	118
69	105
70	104
71	95