A256189 - cp's OEIS frontend

A256189 a(n) = n if n <= 3, otherwise a(n) is the smallest number not occurring earlier such that gcd(a(n-2), a(n)) is a prime and gcd(a(n-1), a(n)) = 1.

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	10
7	21
8	5
9	6
10	25
11	8
12	15
13	14
14	27
15	7
16	12
17	35
18	22
19	45
20	11
21	20
22	33
23	26
24	51
25	13
26	17
27	39
28	34
29	57
30	16
31	19
32	18
33	95
34	28
35	55
36	38
37	65
38	24
39	85
40	46
41	75
42	23
43	36
44	115
45	58
46	69
47	29
48	30
49	203
50	32
51	49
52	50
53	63
54	44
55	87
56	62
57	81
58	31
59	42
60	155
61	52
62	93
63	70
64	99
65	64
66	77
67	54

[1, 2, 3, 4, 9, 10, 21, 5, 6, 25, 8, 15, 14, 27, 7, 12, 35, 22, 45, 11, 20, 33, 26, 51, 13, 17, 39, 34, 57, 16, 19, 18, 95, 28, 55, 38, 65, 24, 85, 46, 75, 23, 36, 115, 58, 69, 29, 30, 203, 32, 49, 50, 63, 44, 87, 62, 81, 31, 42, 155, 52, 93, 70, 99, 64, 77, 54]

cp's OEIS Frontend

A256189 a(n) = n if n <= 3, otherwise a(n) is the smallest number not occurring earlier such that gcd(a(n-2), a(n)) is a prime and gcd(a(n-1), a(n)) = 1.

Table of values

List of values

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	10
7	21
8	5
9	6
10	25
11	8
12	15
13	14
14	27
15	7
16	12
17	35
18	22
19	45
20	11
21	20
22	33
23	26
24	51
25	13
26	17
27	39
28	34
29	57
30	16
31	19
32	18
33	95
34	28
35	55
36	38
37	65
38	24
39	85
40	46
41	75
42	23
43	36
44	115
45	58
46	69
47	29
48	30
49	203
50	32
51	49
52	50
53	63
54	44
55	87
56	62
57	81
58	31
59	42
60	155
61	52
62	93
63	70
64	99
65	64
66	77
67	54

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	10
7	21
8	5
9	6
10	25
11	8
12	15
13	14
14	27
15	7
16	12
17	35
18	22
19	45
20	11
21	20
22	33
23	26
24	51
25	13
26	17
27	39
28	34
29	57
30	16
31	19
32	18
33	95
34	28
35	55
36	38
37	65
38	24
39	85
40	46
41	75
42	23
43	36
44	115
45	58
46	69
47	29
48	30
49	203
50	32
51	49
52	50
53	63
54	44
55	87
56	62
57	81
58	31
59	42
60	155
61	52
62	93
63	70
64	99
65	64
66	77
67	54

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	10
7	21
8	5
9	6
10	25
11	8
12	15
13	14
14	27
15	7
16	12
17	35
18	22
19	45
20	11
21	20
22	33
23	26
24	51
25	13
26	17
27	39
28	34
29	57
30	16
31	19
32	18
33	95
34	28
35	55
36	38
37	65
38	24
39	85
40	46
41	75
42	23
43	36
44	115
45	58
46	69
47	29
48	30
49	203
50	32
51	49
52	50
53	63
54	44
55	87
56	62
57	81
58	31
59	42
60	155
61	52
62	93
63	70
64	99
65	64
66	77
67	54