A075593 - cp's OEIS frontend

A075593 a(1) = 1, a(2n) = prime, a(2n+1) = composite and sum of two successive terms is alternately composite or prime.

n	a(n)
1	1
2	3
3	4
4	2
5	9
6	5
7	6
8	19
9	10
10	11
11	8
12	7
13	12
14	13
15	16
16	17
17	14
18	31
19	22
20	23
21	18
22	37
23	24
24	41
25	20
26	29
27	30
28	47
29	26
30	43
31	28
32	53
33	36
34	59
35	38
36	61
37	40
38	71
39	32
40	67
41	34
42	83
43	44
44	73
45	54
46	79
47	48
48	97
49	42
50	101
51	50
52	103
53	46
54	89
55	60
56	109
57	58
58	107
59	56
60	113
61	66
62	137
63	62
64	127
65	52
66	131
67	68
68	139
69	72

[1, 3, 4, 2, 9, 5, 6, 19, 10, 11, 8, 7, 12, 13, 16, 17, 14, 31, 22, 23, 18, 37, 24, 41, 20, 29, 30, 47, 26, 43, 28, 53, 36, 59, 38, 61, 40, 71, 32, 67, 34, 83, 44, 73, 54, 79, 48, 97, 42, 101, 50, 103, 46, 89, 60, 109, 58, 107, 56, 113, 66, 137, 62, 127, 52, 131, 68, 139, 72]

cp's OEIS Frontend

A075593 a(1) = 1, a(2n) = prime, a(2n+1) = composite and sum of two successive terms is alternately composite or prime.

Table of values

List of values

n	a(n)
1	1
2	3
3	4
4	2
5	9
6	5
7	6
8	19
9	10
10	11
11	8
12	7
13	12
14	13
15	16
16	17
17	14
18	31
19	22
20	23
21	18
22	37
23	24
24	41
25	20
26	29
27	30
28	47
29	26
30	43
31	28
32	53
33	36
34	59
35	38
36	61
37	40
38	71
39	32
40	67
41	34
42	83
43	44
44	73
45	54
46	79
47	48
48	97
49	42
50	101
51	50
52	103
53	46
54	89
55	60
56	109
57	58
58	107
59	56
60	113
61	66
62	137
63	62
64	127
65	52
66	131
67	68
68	139
69	72

n	a(n)
1	1
2	3
3	4
4	2
5	9
6	5
7	6
8	19
9	10
10	11
11	8
12	7
13	12
14	13
15	16
16	17
17	14
18	31
19	22
20	23
21	18
22	37
23	24
24	41
25	20
26	29
27	30
28	47
29	26
30	43
31	28
32	53
33	36
34	59
35	38
36	61
37	40
38	71
39	32
40	67
41	34
42	83
43	44
44	73
45	54
46	79
47	48
48	97
49	42
50	101
51	50
52	103
53	46
54	89
55	60
56	109
57	58
58	107
59	56
60	113
61	66
62	137
63	62
64	127
65	52
66	131
67	68
68	139
69	72

n	a(n)
1	1
2	3
3	4
4	2
5	9
6	5
7	6
8	19
9	10
10	11
11	8
12	7
13	12
14	13
15	16
16	17
17	14
18	31
19	22
20	23
21	18
22	37
23	24
24	41
25	20
26	29
27	30
28	47
29	26
30	43
31	28
32	53
33	36
34	59
35	38
36	61
37	40
38	71
39	32
40	67
41	34
42	83
43	44
44	73
45	54
46	79
47	48
48	97
49	42
50	101
51	50
52	103
53	46
54	89
55	60
56	109
57	58
58	107
59	56
60	113
61	66
62	137
63	62
64	127
65	52
66	131
67	68
68	139
69	72