A075242 - cp's OEIS frontend

A075242 Least base for which the n-th composite number whose reversal in that base is a prime, or zero if impossible.

n	a(n)
1	0
2	2
3	4
4	6
5	2
6	2
7	2
8	3
9	8
10	3
11	2
12	3
13	2
14	2
15	2
16	2
17	9
18	2
19	6
20	4
21	3
22	2
23	3
24	12
25	6
26	3
27	2
28	6
29	2
30	3
31	2
32	2
33	3
34	2
35	9
36	2
37	3
38	2
39	2
40	3
41	2
42	12
43	2
44	3
45	12
46	3
47	6
48	2
49	3
50	10
51	6
52	2
53	3
54	10
55	2
56	26
57	2
58	27
59	2
60	12
61	3
62	2
63	9
64	2
65	12
66	2
67	2
68	3
69	2
70	3
71	2
72	4
73	3
74	2
75	34
76	2
77	3
78	2
79	6
80	2
81	3
82	2
83	38
84	2
85	2
86	3
87	4
88	7
89	24
90	2
91	2
92	3
93	2
94	3
95	18
96	4
97	18

[0, 2, 4, 6, 2, 2, 2, 3, 8, 3, 2, 3, 2, 2, 2, 2, 9, 2, 6, 4, 3, 2, 3, 12, 6, 3, 2, 6, 2, 3, 2, 2, 3, 2, 9, 2, 3, 2, 2, 3, 2, 12, 2, 3, 12, 3, 6, 2, 3, 10, 6, 2, 3, 10, 2, 26, 2, 27, 2, 12, 3, 2, 9, 2, 12, 2, 2, 3, 2, 3, 2, 4, 3, 2, 34, 2, 3, 2, 6, 2, 3, 2, 38, 2, 2, 3, 4, 7, 24, 2, 2, 3, 2, 3, 18, 4, 18]

cp's OEIS Frontend

A075242 Least base for which the n-th composite number whose reversal in that base is a prime, or zero if impossible.

Table of values

List of values

n	a(n)
1	0
2	2
3	4
4	6
5	2
6	2
7	2
8	3
9	8
10	3
11	2
12	3
13	2
14	2
15	2
16	2
17	9
18	2
19	6
20	4
21	3
22	2
23	3
24	12
25	6
26	3
27	2
28	6
29	2
30	3
31	2
32	2
33	3
34	2
35	9
36	2
37	3
38	2
39	2
40	3
41	2
42	12
43	2
44	3
45	12
46	3
47	6
48	2
49	3
50	10
51	6
52	2
53	3
54	10
55	2
56	26
57	2
58	27
59	2
60	12
61	3
62	2
63	9
64	2
65	12
66	2
67	2
68	3
69	2
70	3
71	2
72	4
73	3
74	2
75	34
76	2
77	3
78	2
79	6
80	2
81	3
82	2
83	38
84	2
85	2
86	3
87	4
88	7
89	24
90	2
91	2
92	3
93	2
94	3
95	18
96	4
97	18

n	a(n)
1	0
2	2
3	4
4	6
5	2
6	2
7	2
8	3
9	8
10	3
11	2
12	3
13	2
14	2
15	2
16	2
17	9
18	2
19	6
20	4
21	3
22	2
23	3
24	12
25	6
26	3
27	2
28	6
29	2
30	3
31	2
32	2
33	3
34	2
35	9
36	2
37	3
38	2
39	2
40	3
41	2
42	12
43	2
44	3
45	12
46	3
47	6
48	2
49	3
50	10
51	6
52	2
53	3
54	10
55	2
56	26
57	2
58	27
59	2
60	12
61	3
62	2
63	9
64	2
65	12
66	2
67	2
68	3
69	2
70	3
71	2
72	4
73	3
74	2
75	34
76	2
77	3
78	2
79	6
80	2
81	3
82	2
83	38
84	2
85	2
86	3
87	4
88	7
89	24
90	2
91	2
92	3
93	2
94	3
95	18
96	4
97	18

n	a(n)
1	0
2	2
3	4
4	6
5	2
6	2
7	2
8	3
9	8
10	3
11	2
12	3
13	2
14	2
15	2
16	2
17	9
18	2
19	6
20	4
21	3
22	2
23	3
24	12
25	6
26	3
27	2
28	6
29	2
30	3
31	2
32	2
33	3
34	2
35	9
36	2
37	3
38	2
39	2
40	3
41	2
42	12
43	2
44	3
45	12
46	3
47	6
48	2
49	3
50	10
51	6
52	2
53	3
54	10
55	2
56	26
57	2
58	27
59	2
60	12
61	3
62	2
63	9
64	2
65	12
66	2
67	2
68	3
69	2
70	3
71	2
72	4
73	3
74	2
75	34
76	2
77	3
78	2
79	6
80	2
81	3
82	2
83	38
84	2
85	2
86	3
87	4
88	7
89	24
90	2
91	2
92	3
93	2
94	3
95	18
96	4
97	18