A066421 - cp's OEIS frontend

A066421 a(n) = least k > 0 such that sigma^(k)(n) + 1 is prime, if such k exists; otherwise 0, where sigma^(k) denotes application of sigma k times.

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

[1, 2, 1, 5, 1, 1, 4, 3, 4, 1, 1, 1, 3, 2, 2, 5, 1, 5, 2, 1, 4, 1, 2, 1, 5, 1, 1, 4, 1, 1, 4, 3, 9, 4, 9, 2, 2, 1, 4, 3, 1, 1, 9, 8, 1, 1, 9, 8, 5, 4, 1, 5, 4, 3, 1, 3, 4, 3, 1, 4, 2, 1, 2, 4, 8, 3, 2, 1, 1, 3, 1, 2, 3, 2, 8, 2, 1, 4, 4, 3, 4, 1, 8, 7, 1, 2, 3, 1, 3, 2, 1, 4, 3, 3, 3, 4, 5, 4, 1, 2]

cp's OEIS Frontend

A066421 a(n) = least k > 0 such that sigma^(k)(n) + 1 is prime, if such k exists; otherwise 0, where sigma^(k) denotes application of sigma k times.

Table of values

List of values

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

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

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