A356431 - cp's OEIS frontend

A356431 a(1) = 1, a(2) = 2; for n > 2, a(n) is the smallest positive number not occurring earlier that shares a factor with both a(n-1) and the number of divisors of a(n-1).

n	a(n)
1	1
2	2
3	4
4	6
5	8
6	10
7	12
8	3
9	18
10	9
11	15
12	20
13	14
14	16
15	30
16	22
17	24
18	26
19	28
20	21
21	36
22	27
23	42
24	32
25	34
26	38
27	40
28	44
29	33
30	48
31	45
32	39
33	52
34	46
35	50
36	54
37	56
38	58
39	60
40	51
41	66
42	62
43	64
44	70
45	68
46	72
47	57
48	76
49	74
50	78
51	80
52	5
53	90
54	63
55	69
56	84
57	75
58	81
59	105
60	96
61	82
62	86
63	88
64	92
65	94
66	98
67	100
68	102
69	104
70	106
71	108
72	87
73	114
74	110

[1, 2, 4, 6, 8, 10, 12, 3, 18, 9, 15, 20, 14, 16, 30, 22, 24, 26, 28, 21, 36, 27, 42, 32, 34, 38, 40, 44, 33, 48, 45, 39, 52, 46, 50, 54, 56, 58, 60, 51, 66, 62, 64, 70, 68, 72, 57, 76, 74, 78, 80, 5, 90, 63, 69, 84, 75, 81, 105, 96, 82, 86, 88, 92, 94, 98, 100, 102, 104, 106, 108, 87, 114, 110]

cp's OEIS Frontend

A356431 a(1) = 1, a(2) = 2; for n > 2, a(n) is the smallest positive number not occurring earlier that shares a factor with both a(n-1) and the number of divisors of a(n-1).

Table of values

List of values

n	a(n)
1	1
2	2
3	4
4	6
5	8
6	10
7	12
8	3
9	18
10	9
11	15
12	20
13	14
14	16
15	30
16	22
17	24
18	26
19	28
20	21
21	36
22	27
23	42
24	32
25	34
26	38
27	40
28	44
29	33
30	48
31	45
32	39
33	52
34	46
35	50
36	54
37	56
38	58
39	60
40	51
41	66
42	62
43	64
44	70
45	68
46	72
47	57
48	76
49	74
50	78
51	80
52	5
53	90
54	63
55	69
56	84
57	75
58	81
59	105
60	96
61	82
62	86
63	88
64	92
65	94
66	98
67	100
68	102
69	104
70	106
71	108
72	87
73	114
74	110

n	a(n)
1	1
2	2
3	4
4	6
5	8
6	10
7	12
8	3
9	18
10	9
11	15
12	20
13	14
14	16
15	30
16	22
17	24
18	26
19	28
20	21
21	36
22	27
23	42
24	32
25	34
26	38
27	40
28	44
29	33
30	48
31	45
32	39
33	52
34	46
35	50
36	54
37	56
38	58
39	60
40	51
41	66
42	62
43	64
44	70
45	68
46	72
47	57
48	76
49	74
50	78
51	80
52	5
53	90
54	63
55	69
56	84
57	75
58	81
59	105
60	96
61	82
62	86
63	88
64	92
65	94
66	98
67	100
68	102
69	104
70	106
71	108
72	87
73	114
74	110

n	a(n)
1	1
2	2
3	4
4	6
5	8
6	10
7	12
8	3
9	18
10	9
11	15
12	20
13	14
14	16
15	30
16	22
17	24
18	26
19	28
20	21
21	36
22	27
23	42
24	32
25	34
26	38
27	40
28	44
29	33
30	48
31	45
32	39
33	52
34	46
35	50
36	54
37	56
38	58
39	60
40	51
41	66
42	62
43	64
44	70
45	68
46	72
47	57
48	76
49	74
50	78
51	80
52	5
53	90
54	63
55	69
56	84
57	75
58	81
59	105
60	96
61	82
62	86
63	88
64	92
65	94
66	98
67	100
68	102
69	104
70	106
71	108
72	87
73	114
74	110