A228323 - cp's OEIS frontend

A228323 a(1)=1; thereafter a(n) is the smallest number m not yet in the sequence such that at least one of the concatenations a(n-1)||m or m||a(n-1) is prime.

n	a(n)
1	1
2	3
3	2
4	9
5	5
6	21
7	4
8	7
9	6
10	13
11	10
12	19
13	16
14	27
15	8
16	11
17	15
18	23
19	12
20	17
21	20
22	29
23	14
24	33
25	26
26	47
27	18
28	31
29	25
30	39
31	22
32	37
33	24
34	41
35	30
36	49
37	34
38	57
39	28
40	43
41	36
42	59
43	32
44	51
45	38
46	53
47	42
48	61
49	45
50	67
51	58
52	69
53	55
54	63
55	44
56	81
57	35
58	71
59	48
60	77
61	50
62	87
63	62
64	99
65	40
66	73
67	46

[1, 3, 2, 9, 5, 21, 4, 7, 6, 13, 10, 19, 16, 27, 8, 11, 15, 23, 12, 17, 20, 29, 14, 33, 26, 47, 18, 31, 25, 39, 22, 37, 24, 41, 30, 49, 34, 57, 28, 43, 36, 59, 32, 51, 38, 53, 42, 61, 45, 67, 58, 69, 55, 63, 44, 81, 35, 71, 48, 77, 50, 87, 62, 99, 40, 73, 46]

cp's OEIS Frontend

A228323 a(1)=1; thereafter a(n) is the smallest number m not yet in the sequence such that at least one of the concatenations a(n-1)||m or m||a(n-1) is prime.

Table of values

List of values

n	a(n)
1	1
2	3
3	2
4	9
5	5
6	21
7	4
8	7
9	6
10	13
11	10
12	19
13	16
14	27
15	8
16	11
17	15
18	23
19	12
20	17
21	20
22	29
23	14
24	33
25	26
26	47
27	18
28	31
29	25
30	39
31	22
32	37
33	24
34	41
35	30
36	49
37	34
38	57
39	28
40	43
41	36
42	59
43	32
44	51
45	38
46	53
47	42
48	61
49	45
50	67
51	58
52	69
53	55
54	63
55	44
56	81
57	35
58	71
59	48
60	77
61	50
62	87
63	62
64	99
65	40
66	73
67	46

n	a(n)
1	1
2	3
3	2
4	9
5	5
6	21
7	4
8	7
9	6
10	13
11	10
12	19
13	16
14	27
15	8
16	11
17	15
18	23
19	12
20	17
21	20
22	29
23	14
24	33
25	26
26	47
27	18
28	31
29	25
30	39
31	22
32	37
33	24
34	41
35	30
36	49
37	34
38	57
39	28
40	43
41	36
42	59
43	32
44	51
45	38
46	53
47	42
48	61
49	45
50	67
51	58
52	69
53	55
54	63
55	44
56	81
57	35
58	71
59	48
60	77
61	50
62	87
63	62
64	99
65	40
66	73
67	46

n	a(n)
1	1
2	3
3	2
4	9
5	5
6	21
7	4
8	7
9	6
10	13
11	10
12	19
13	16
14	27
15	8
16	11
17	15
18	23
19	12
20	17
21	20
22	29
23	14
24	33
25	26
26	47
27	18
28	31
29	25
30	39
31	22
32	37
33	24
34	41
35	30
36	49
37	34
38	57
39	28
40	43
41	36
42	59
43	32
44	51
45	38
46	53
47	42
48	61
49	45
50	67
51	58
52	69
53	55
54	63
55	44
56	81
57	35
58	71
59	48
60	77
61	50
62	87
63	62
64	99
65	40
66	73
67	46