A303978 - cp's OEIS frontend

A303978 a(n) is the smallest prime p that does not divide n-1 such that (n^p-1)/(n-1) is composite, for n > 1.

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

[11, 5, 5, 5, 11, 7, 2, 3, 5, 3, 7, 11, 2, 5, 7, 13, 3, 5, 2, 7, 11, 3, 2, 5, 2, 5, 7, 3, 3, 11, 2, 5, 2, 3, 3, 5, 2, 3, 11, 7, 3, 11, 2, 3, 11, 3, 2, 5, 2, 3, 5, 3, 2, 5, 2, 5, 5, 5, 3, 11, 2, 3, 2, 3, 11, 5, 2, 5, 5, 11, 3, 11, 2, 5, 2, 7, 5, 7, 2, 3, 5, 3, 2, 11, 2, 3, 5, 5, 2]

cp's OEIS Frontend

A303978 a(n) is the smallest prime p that does not divide n-1 such that (n^p-1)/(n-1) is composite, for n > 1.

Table of values

List of values

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

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

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