A373860 - cp's OEIS frontend

A373860 a(n) = n for n <= 4; for n > 4, a(n) is the smallest unused positive number that shares a factor with the most recently appearing even number prior to a(n-1) if a(n-1) is even, otherwise it shares a factor with the most recently appearing odd number prior to a(n-1) if a(n-1) is odd.

n	a(n)
1	1
2	2
3	3
4	4
5	6
6	8
7	9
8	12
9	10
10	14
11	5
12	15
13	20
14	7
15	18
16	16
17	21
18	28
19	22
20	24
21	11
22	27
23	33
24	30
25	26
26	25
27	36
28	13
29	35
30	39
31	40
32	32
33	34
34	38
35	17
36	42
37	19
38	51
39	57
40	45
41	48
42	44
43	46
44	50
45	23
46	54
47	52
48	56
49	58
50	49
51	69
52	63
53	60
54	29
55	66
56	55
57	87
58	65
59	72
60	62
61	64
62	31
63	70
64	68
65	74
66	76
67	37
68	93
69	111
70	75
71	78
72	80
73	81
74	84
75	82
76	77
77	90

[1, 2, 3, 4, 6, 8, 9, 12, 10, 14, 5, 15, 20, 7, 18, 16, 21, 28, 22, 24, 11, 27, 33, 30, 26, 25, 36, 13, 35, 39, 40, 32, 34, 38, 17, 42, 19, 51, 57, 45, 48, 44, 46, 50, 23, 54, 52, 56, 58, 49, 69, 63, 60, 29, 66, 55, 87, 65, 72, 62, 64, 31, 70, 68, 74, 76, 37, 93, 111, 75, 78, 80, 81, 84, 82, 77, 90]

cp's OEIS Frontend

A373860 a(n) = n for n <= 4; for n > 4, a(n) is the smallest unused positive number that shares a factor with the most recently appearing even number prior to a(n-1) if a(n-1) is even, otherwise it shares a factor with the most recently appearing odd number prior to a(n-1) if a(n-1) is odd.

Table of values

List of values

n	a(n)
1	1
2	2
3	3
4	4
5	6
6	8
7	9
8	12
9	10
10	14
11	5
12	15
13	20
14	7
15	18
16	16
17	21
18	28
19	22
20	24
21	11
22	27
23	33
24	30
25	26
26	25
27	36
28	13
29	35
30	39
31	40
32	32
33	34
34	38
35	17
36	42
37	19
38	51
39	57
40	45
41	48
42	44
43	46
44	50
45	23
46	54
47	52
48	56
49	58
50	49
51	69
52	63
53	60
54	29
55	66
56	55
57	87
58	65
59	72
60	62
61	64
62	31
63	70
64	68
65	74
66	76
67	37
68	93
69	111
70	75
71	78
72	80
73	81
74	84
75	82
76	77
77	90

n	a(n)
1	1
2	2
3	3
4	4
5	6
6	8
7	9
8	12
9	10
10	14
11	5
12	15
13	20
14	7
15	18
16	16
17	21
18	28
19	22
20	24
21	11
22	27
23	33
24	30
25	26
26	25
27	36
28	13
29	35
30	39
31	40
32	32
33	34
34	38
35	17
36	42
37	19
38	51
39	57
40	45
41	48
42	44
43	46
44	50
45	23
46	54
47	52
48	56
49	58
50	49
51	69
52	63
53	60
54	29
55	66
56	55
57	87
58	65
59	72
60	62
61	64
62	31
63	70
64	68
65	74
66	76
67	37
68	93
69	111
70	75
71	78
72	80
73	81
74	84
75	82
76	77
77	90

n	a(n)
1	1
2	2
3	3
4	4
5	6
6	8
7	9
8	12
9	10
10	14
11	5
12	15
13	20
14	7
15	18
16	16
17	21
18	28
19	22
20	24
21	11
22	27
23	33
24	30
25	26
26	25
27	36
28	13
29	35
30	39
31	40
32	32
33	34
34	38
35	17
36	42
37	19
38	51
39	57
40	45
41	48
42	44
43	46
44	50
45	23
46	54
47	52
48	56
49	58
50	49
51	69
52	63
53	60
54	29
55	66
56	55
57	87
58	65
59	72
60	62
61	64
62	31
63	70
64	68
65	74
66	76
67	37
68	93
69	111
70	75
71	78
72	80
73	81
74	84
75	82
76	77
77	90