A243625 - cp's OEIS frontend

A243625 a(n) is the smallest positive integer not already in the sequence for which a(n)+a(n-1) is a semiprime, with a(1)=1.

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

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

cp's OEIS Frontend

A243625 a(n) is the smallest positive integer not already in the sequence for which a(n)+a(n-1) is a semiprime, with a(1)=1.

Table of values

List of values

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

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

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