A337181 - cp's OEIS frontend

A337181 a(1) = 1, a(2) = 2; for n>2, a(n) is the smallest number not already used that is a multiple of at least one prime factor of both a(n-1) and a(n-2).

n	a(n)
1	1
2	2
3	4
4	8
5	12
6	6
7	9
8	18
9	24
10	16
11	20
12	10
13	25
14	30
15	15
16	27
17	36
18	42
19	14
20	21
21	28
22	48
23	32
24	40
25	44
26	22
27	52
28	26
29	56
30	60
31	35
32	45
33	50
34	54
35	64
36	66
37	68
38	34
39	72
40	51
41	63
42	81
43	84
44	78
45	39
46	90
47	65
48	70
49	75
50	80
51	96
52	76
53	38
54	88
55	92
56	46
57	100
58	104
59	108
60	102
61	99
62	33
63	117
64	126
65	91
66	49
67	98
68	112
69	116
70	58
71	120

[1, 2, 4, 8, 12, 6, 9, 18, 24, 16, 20, 10, 25, 30, 15, 27, 36, 42, 14, 21, 28, 48, 32, 40, 44, 22, 52, 26, 56, 60, 35, 45, 50, 54, 64, 66, 68, 34, 72, 51, 63, 81, 84, 78, 39, 90, 65, 70, 75, 80, 96, 76, 38, 88, 92, 46, 100, 104, 108, 102, 99, 33, 117, 126, 91, 49, 98, 112, 116, 58, 120]

cp's OEIS Frontend

A337181 a(1) = 1, a(2) = 2; for n>2, a(n) is the smallest number not already used that is a multiple of at least one prime factor of both a(n-1) and a(n-2).

Table of values

List of values

n	a(n)
1	1
2	2
3	4
4	8
5	12
6	6
7	9
8	18
9	24
10	16
11	20
12	10
13	25
14	30
15	15
16	27
17	36
18	42
19	14
20	21
21	28
22	48
23	32
24	40
25	44
26	22
27	52
28	26
29	56
30	60
31	35
32	45
33	50
34	54
35	64
36	66
37	68
38	34
39	72
40	51
41	63
42	81
43	84
44	78
45	39
46	90
47	65
48	70
49	75
50	80
51	96
52	76
53	38
54	88
55	92
56	46
57	100
58	104
59	108
60	102
61	99
62	33
63	117
64	126
65	91
66	49
67	98
68	112
69	116
70	58
71	120

n	a(n)
1	1
2	2
3	4
4	8
5	12
6	6
7	9
8	18
9	24
10	16
11	20
12	10
13	25
14	30
15	15
16	27
17	36
18	42
19	14
20	21
21	28
22	48
23	32
24	40
25	44
26	22
27	52
28	26
29	56
30	60
31	35
32	45
33	50
34	54
35	64
36	66
37	68
38	34
39	72
40	51
41	63
42	81
43	84
44	78
45	39
46	90
47	65
48	70
49	75
50	80
51	96
52	76
53	38
54	88
55	92
56	46
57	100
58	104
59	108
60	102
61	99
62	33
63	117
64	126
65	91
66	49
67	98
68	112
69	116
70	58
71	120

n	a(n)
1	1
2	2
3	4
4	8
5	12
6	6
7	9
8	18
9	24
10	16
11	20
12	10
13	25
14	30
15	15
16	27
17	36
18	42
19	14
20	21
21	28
22	48
23	32
24	40
25	44
26	22
27	52
28	26
29	56
30	60
31	35
32	45
33	50
34	54
35	64
36	66
37	68
38	34
39	72
40	51
41	63
42	81
43	84
44	78
45	39
46	90
47	65
48	70
49	75
50	80
51	96
52	76
53	38
54	88
55	92
56	46
57	100
58	104
59	108
60	102
61	99
62	33
63	117
64	126
65	91
66	49
67	98
68	112
69	116
70	58
71	120