A090465 - cp's OEIS frontend

A090465 Smallest number m such that (n+1)*10^m-1 (i.e., n with m nines appended) yields a prime, or -1 if this will always yield a composite number.

n	a(n)
1	1
2	0
3	0
4	2
5	0
6	-1
7	0
8	1
9	-1
10	1
11	0
12	-1
13	0
14	1
15	-1
16	2
17	0
18	-1
19	0
20	2
21	-1
22	1
23	0
24	-1
25	3
26	1
27	-1
28	4
29	0
30	-1
31	0
32	2
33	-1
34	1
35	1
36	-1
37	0
38	1
39	-1
40	1
41	0
42	-1
43	0
44	1
45	-1
46	16
47	0
48	-1
49	1
50	1
51	-1
52	3
53	0
54	-1
55	5
56	1
57	-1
58	15
59	0
60	-1
61	0
62	2
63	-1
64	12
65	1
66	-1
67	0
68	2
69	-1
70	1
71	0
72	-1
73	0
74	2
75	-1
76	1
77	3
78	-1
79	0
80	1
81	-1
82	1
83	0
84	-1
85	1
86	2
87	-1
88	33
89	0
90	-1
91	1
92	1
93	-1
94	3
95	10
96	-1
97	0
98	3
99	-1
100	1
101	0
102	-1
103	0
104	1
105	-1
106	1
107	0
108	-1

[1, 0, 0, 2, 0, -1, 0, 1, -1, 1, 0, -1, 0, 1, -1, 2, 0, -1, 0, 2, -1, 1, 0, -1, 3, 1, -1, 4, 0, -1, 0, 2, -1, 1, 1, -1, 0, 1, -1, 1, 0, -1, 0, 1, -1, 16, 0, -1, 1, 1, -1, 3, 0, -1, 5, 1, -1, 15, 0, -1, 0, 2, -1, 12, 1, -1, 0, 2, -1, 1, 0, -1, 0, 2, -1, 1, 3, -1, 0, 1, -1, 1, 0, -1, 1, 2, -1, 33, 0, -1, 1, 1, -1, 3, 10, -1, 0, 3, -1, 1, 0, -1, 0, 1, -1, 1, 0, -1]

cp's OEIS Frontend

A090465 Smallest number m such that (n+1)*10^m-1 (i.e., n with m nines appended) yields a prime, or -1 if this will always yield a composite number.

Table of values

List of values

n	a(n)
1	1
2	0
3	0
4	2
5	0
6	-1
7	0
8	1
9	-1
10	1
11	0
12	-1
13	0
14	1
15	-1
16	2
17	0
18	-1
19	0
20	2
21	-1
22	1
23	0
24	-1
25	3
26	1
27	-1
28	4
29	0
30	-1
31	0
32	2
33	-1
34	1
35	1
36	-1
37	0
38	1
39	-1
40	1
41	0
42	-1
43	0
44	1
45	-1
46	16
47	0
48	-1
49	1
50	1
51	-1
52	3
53	0
54	-1
55	5
56	1
57	-1
58	15
59	0
60	-1
61	0
62	2
63	-1
64	12
65	1
66	-1
67	0
68	2
69	-1
70	1
71	0
72	-1
73	0
74	2
75	-1
76	1
77	3
78	-1
79	0
80	1
81	-1
82	1
83	0
84	-1
85	1
86	2
87	-1
88	33
89	0
90	-1
91	1
92	1
93	-1
94	3
95	10
96	-1
97	0
98	3
99	-1
100	1
101	0
102	-1
103	0
104	1
105	-1
106	1
107	0
108	-1

n	a(n)
1	1
2	0
3	0
4	2
5	0
6	-1
7	0
8	1
9	-1
10	1
11	0
12	-1
13	0
14	1
15	-1
16	2
17	0
18	-1
19	0
20	2
21	-1
22	1
23	0
24	-1
25	3
26	1
27	-1
28	4
29	0
30	-1
31	0
32	2
33	-1
34	1
35	1
36	-1
37	0
38	1
39	-1
40	1
41	0
42	-1
43	0
44	1
45	-1
46	16
47	0
48	-1
49	1
50	1
51	-1
52	3
53	0
54	-1
55	5
56	1
57	-1
58	15
59	0
60	-1
61	0
62	2
63	-1
64	12
65	1
66	-1
67	0
68	2
69	-1
70	1
71	0
72	-1
73	0
74	2
75	-1
76	1
77	3
78	-1
79	0
80	1
81	-1
82	1
83	0
84	-1
85	1
86	2
87	-1
88	33
89	0
90	-1
91	1
92	1
93	-1
94	3
95	10
96	-1
97	0
98	3
99	-1
100	1
101	0
102	-1
103	0
104	1
105	-1
106	1
107	0
108	-1

n	a(n)
1	1
2	0
3	0
4	2
5	0
6	-1
7	0
8	1
9	-1
10	1
11	0
12	-1
13	0
14	1
15	-1
16	2
17	0
18	-1
19	0
20	2
21	-1
22	1
23	0
24	-1
25	3
26	1
27	-1
28	4
29	0
30	-1
31	0
32	2
33	-1
34	1
35	1
36	-1
37	0
38	1
39	-1
40	1
41	0
42	-1
43	0
44	1
45	-1
46	16
47	0
48	-1
49	1
50	1
51	-1
52	3
53	0
54	-1
55	5
56	1
57	-1
58	15
59	0
60	-1
61	0
62	2
63	-1
64	12
65	1
66	-1
67	0
68	2
69	-1
70	1
71	0
72	-1
73	0
74	2
75	-1
76	1
77	3
78	-1
79	0
80	1
81	-1
82	1
83	0
84	-1
85	1
86	2
87	-1
88	33
89	0
90	-1
91	1
92	1
93	-1
94	3
95	10
96	-1
97	0
98	3
99	-1
100	1
101	0
102	-1
103	0
104	1
105	-1
106	1
107	0
108	-1