A143691 - cp's OEIS frontend

A143691 Lexicographically earliest permutation of the natural numbers having alternating even and odd numbers of prime factors.

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

[1, 2, 4, 3, 6, 5, 9, 7, 10, 8, 14, 11, 15, 12, 16, 13, 21, 17, 22, 18, 24, 19, 25, 20, 26, 23, 33, 27, 34, 28, 35, 29, 36, 30, 38, 31, 39, 32, 40, 37, 46, 41, 49, 42, 51, 43, 54, 44, 55, 45, 56, 47, 57, 48, 58, 50, 60, 52, 62, 53, 64, 59, 65, 61, 69, 63, 74, 66, 77, 67, 81, 68]

cp's OEIS Frontend

A143691 Lexicographically earliest permutation of the natural numbers having alternating even and odd numbers of prime factors.

Table of values

List of values

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

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

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