A374163 - cp's OEIS frontend

A374163 a(1) = 1; for n>1 a(n) is the minimum value of k > 0 such that sigma^{k}(n)-1 is prime, if such a k exists; otherwise -1, where sigma^{k} is the k-th iteration of sigma=A000203.

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

[1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 4, 1, 1, 1, 2, 1, 4, 1, 1, 1, 5, 1, 1, 2, 1, 2, 3, 1, 1, 1, 2, 1, 1, 1, 4, 1, 1, 3, 1, 1, 2, 1, 1, 2, 1, 1, 2, 2, 2, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 7, 1, 2, 2, 7, 1, 3, 1, 1, 2, 1, 2, 1, 1, 2, 8, 2, 1, 1, 1, 1, 2, 1, 1, 1, 3, 1, 1, 7, 2]

cp's OEIS Frontend

A374163 a(1) = 1; for n>1 a(n) is the minimum value of k > 0 such that sigma^{k}(n)-1 is prime, if such a k exists; otherwise -1, where sigma^{k} is the k-th iteration of sigma=A000203.

Table of values

List of values

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

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

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