A269252 - cp's OEIS frontend

A269252 Define a sequence by s(k) = n*s(k-1) - s(k-2), with s(0) = 1, s(1) = n - 1. a(n) is the smallest index k such that s(k) is prime, or -1 if no such k exists.

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

[-1, -1, 1, 1, 2, 1, 2, 1, 2, 2, 2, 1, 3, 1, 3, 2, 2, 1, 14, 1, 2, 2, 3, 1, 2, 5, 2, 36, 2, 1, 2, 1, 15, -1, 6, 2, 3, 1, 2, 2, 6, 1, 3, 1, 2, 2, 2, 1, 2, 3, 2, -1, 3, 1, 2, 2, 2, 6, 3, 1, 2, 1, 30, 3, 2, 2, 2, 1, 2, 5, 2, 1, 5, 1, 6, 3, 2, 6, 3, 1, 8, 6, 14, 1, 3]

cp's OEIS Frontend

A269252 Define a sequence by s(k) = n*s(k-1) - s(k-2), with s(0) = 1, s(1) = n - 1. a(n) is the smallest index k such that s(k) is prime, or -1 if no such k exists.

Table of values

List of values

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

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

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