A257862 - cp's OEIS frontend

A257862 a(n) = n if n <= 3, otherwise a(n) is the smallest number not already used and relatively prime to a(n-1) such that the set of prime divisors of one of the numbers {a(n-2), a(n)} is a subset of the set of prime divisors of the other.

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	8
7	15
8	14
9	5
10	7
11	10
12	21
13	16
14	27
15	20
16	33
17	25
18	11
19	30
20	77
21	6
22	49
23	12
24	35
25	18
26	125
27	24
28	55
29	32
30	121
31	26
32	99
33	13
34	66
35	65
36	22
37	169
38	44
39	39
40	64
41	81
42	28
43	45
44	56
45	75
46	98
47	135
48	112
49	165
50	128
51	225
52	34
53	105
54	17
55	63
56	68
57	147
58	136
59	189
60	170
61	231
62	40
63	243
64	50

[1, 2, 3, 4, 9, 8, 15, 14, 5, 7, 10, 21, 16, 27, 20, 33, 25, 11, 30, 77, 6, 49, 12, 35, 18, 125, 24, 55, 32, 121, 26, 99, 13, 66, 65, 22, 169, 44, 39, 64, 81, 28, 45, 56, 75, 98, 135, 112, 165, 128, 225, 34, 105, 17, 63, 68, 147, 136, 189, 170, 231, 40, 243, 50]

cp's OEIS Frontend

A257862 a(n) = n if n <= 3, otherwise a(n) is the smallest number not already used and relatively prime to a(n-1) such that the set of prime divisors of one of the numbers {a(n-2), a(n)} is a subset of the set of prime divisors of the other.

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	7
11	10
12	21
13	16
14	27
15	20
16	33
17	25
18	11
19	30
20	77
21	6
22	49
23	12
24	35
25	18
26	125
27	24
28	55
29	32
30	121
31	26
32	99
33	13
34	66
35	65
36	22
37	169
38	44
39	39
40	64
41	81
42	28
43	45
44	56
45	75
46	98
47	135
48	112
49	165
50	128
51	225
52	34
53	105
54	17
55	63
56	68
57	147
58	136
59	189
60	170
61	231
62	40
63	243
64	50

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	8
7	15
8	14
9	5
10	7
11	10
12	21
13	16
14	27
15	20
16	33
17	25
18	11
19	30
20	77
21	6
22	49
23	12
24	35
25	18
26	125
27	24
28	55
29	32
30	121
31	26
32	99
33	13
34	66
35	65
36	22
37	169
38	44
39	39
40	64
41	81
42	28
43	45
44	56
45	75
46	98
47	135
48	112
49	165
50	128
51	225
52	34
53	105
54	17
55	63
56	68
57	147
58	136
59	189
60	170
61	231
62	40
63	243
64	50

n	a(n)
1	1
2	2
3	3
4	4
5	9
6	8
7	15
8	14
9	5
10	7
11	10
12	21
13	16
14	27
15	20
16	33
17	25
18	11
19	30
20	77
21	6
22	49
23	12
24	35
25	18
26	125
27	24
28	55
29	32
30	121
31	26
32	99
33	13
34	66
35	65
36	22
37	169
38	44
39	39
40	64
41	81
42	28
43	45
44	56
45	75
46	98
47	135
48	112
49	165
50	128
51	225
52	34
53	105
54	17
55	63
56	68
57	147
58	136
59	189
60	170
61	231
62	40
63	243
64	50