A373999 - cp's OEIS frontend

A373999 a(1) = 1, a(2) = 2, a(3) = 3, a(4) = 5, a(5) = 7; for n > 5, a(n) is the smallest unused positive number that is coprime to a(n-1), a(n-2) and a(n-3) but has a common factor with at least one of a(1)...a(n-4).

n	a(n)
1	1
2	2
3	3
4	5
5	7
6	4
7	9
8	25
9	49
10	8
11	27
12	55
13	91
14	16
15	51
16	11
17	13
18	10
19	17
20	21
21	121
22	20
23	169
24	57
25	77
26	32
27	65
28	19
29	33
30	14
31	85
32	247
33	69
34	22
35	35
36	221
37	23
38	6
39	95
40	119
41	143
42	12
43	115
44	133
45	187
46	18
47	125
48	161
49	209
50	24
51	145
52	217
53	253
54	26
55	15
56	29
57	31
58	28
59	39
60	185
61	289
62	38
63	63
64	37
65	155
66	34
67	81
68	203
69	205
70	44

[1, 2, 3, 5, 7, 4, 9, 25, 49, 8, 27, 55, 91, 16, 51, 11, 13, 10, 17, 21, 121, 20, 169, 57, 77, 32, 65, 19, 33, 14, 85, 247, 69, 22, 35, 221, 23, 6, 95, 119, 143, 12, 115, 133, 187, 18, 125, 161, 209, 24, 145, 217, 253, 26, 15, 29, 31, 28, 39, 185, 289, 38, 63, 37, 155, 34, 81, 203, 205, 44]

cp's OEIS Frontend

A373999 a(1) = 1, a(2) = 2, a(3) = 3, a(4) = 5, a(5) = 7; for n > 5, a(n) is the smallest unused positive number that is coprime to a(n-1), a(n-2) and a(n-3) but has a common factor with at least one of a(1)...a(n-4).

Table of values

List of values

n	a(n)
1	1
2	2
3	3
4	5
5	7
6	4
7	9
8	25
9	49
10	8
11	27
12	55
13	91
14	16
15	51
16	11
17	13
18	10
19	17
20	21
21	121
22	20
23	169
24	57
25	77
26	32
27	65
28	19
29	33
30	14
31	85
32	247
33	69
34	22
35	35
36	221
37	23
38	6
39	95
40	119
41	143
42	12
43	115
44	133
45	187
46	18
47	125
48	161
49	209
50	24
51	145
52	217
53	253
54	26
55	15
56	29
57	31
58	28
59	39
60	185
61	289
62	38
63	63
64	37
65	155
66	34
67	81
68	203
69	205
70	44

n	a(n)
1	1
2	2
3	3
4	5
5	7
6	4
7	9
8	25
9	49
10	8
11	27
12	55
13	91
14	16
15	51
16	11
17	13
18	10
19	17
20	21
21	121
22	20
23	169
24	57
25	77
26	32
27	65
28	19
29	33
30	14
31	85
32	247
33	69
34	22
35	35
36	221
37	23
38	6
39	95
40	119
41	143
42	12
43	115
44	133
45	187
46	18
47	125
48	161
49	209
50	24
51	145
52	217
53	253
54	26
55	15
56	29
57	31
58	28
59	39
60	185
61	289
62	38
63	63
64	37
65	155
66	34
67	81
68	203
69	205
70	44

n	a(n)
1	1
2	2
3	3
4	5
5	7
6	4
7	9
8	25
9	49
10	8
11	27
12	55
13	91
14	16
15	51
16	11
17	13
18	10
19	17
20	21
21	121
22	20
23	169
24	57
25	77
26	32
27	65
28	19
29	33
30	14
31	85
32	247
33	69
34	22
35	35
36	221
37	23
38	6
39	95
40	119
41	143
42	12
43	115
44	133
45	187
46	18
47	125
48	161
49	209
50	24
51	145
52	217
53	253
54	26
55	15
56	29
57	31
58	28
59	39
60	185
61	289
62	38
63	63
64	37
65	155
66	34
67	81
68	203
69	205
70	44