A291786 - cp's OEIS frontend

A291786 a(n) = number of iterations of k -> (psi(k)+phi(k))/2 (A291784) needed to reach a prime or a power of a prime or 1, or -1 if that doesn't happen.

n	a(n)
1	0
2	0
3	0
4	0
5	0
6	1
7	0
8	0
9	0
10	1
11	0
12	3
13	0
14	2
15	1
16	0
17	0
18	3
19	0
20	2
21	2
22	1
23	0
24	6
25	0
26	1
27	0
28	5
29	0
30	4
31	0
32	0
33	9
34	8
35	7
36	6
37	0
38	5
39	4
40	3
41	0
42	5
43	0
44	2
45	-1
46	1
47	0
48	-1
49	0
50	-1
51	6
52	5
53	0
54	4
55	-1
56	-1
57	2
58	1
59	0
60	-1
61	0
62	4
63	3
64	0
65	3
66	2
67	0
68	-1
69	-1
70	-1
71	0
72	-1
73	0

[0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 3, 0, 2, 1, 0, 0, 3, 0, 2, 2, 1, 0, 6, 0, 1, 0, 5, 0, 4, 0, 0, 9, 8, 7, 6, 0, 5, 4, 3, 0, 5, 0, 2, -1, 1, 0, -1, 0, -1, 6, 5, 0, 4, -1, -1, 2, 1, 0, -1, 0, 4, 3, 0, 3, 2, 0, -1, -1, -1, 0, -1, 0]

cp's OEIS Frontend

A291786 a(n) = number of iterations of k -> (psi(k)+phi(k))/2 (A291784) needed to reach a prime or a power of a prime or 1, or -1 if that doesn't happen.

Table of values

List of values

n	a(n)
1	0
2	0
3	0
4	0
5	0
6	1
7	0
8	0
9	0
10	1
11	0
12	3
13	0
14	2
15	1
16	0
17	0
18	3
19	0
20	2
21	2
22	1
23	0
24	6
25	0
26	1
27	0
28	5
29	0
30	4
31	0
32	0
33	9
34	8
35	7
36	6
37	0
38	5
39	4
40	3
41	0
42	5
43	0
44	2
45	-1
46	1
47	0
48	-1
49	0
50	-1
51	6
52	5
53	0
54	4
55	-1
56	-1
57	2
58	1
59	0
60	-1
61	0
62	4
63	3
64	0
65	3
66	2
67	0
68	-1
69	-1
70	-1
71	0
72	-1
73	0

n	a(n)
1	0
2	0
3	0
4	0
5	0
6	1
7	0
8	0
9	0
10	1
11	0
12	3
13	0
14	2
15	1
16	0
17	0
18	3
19	0
20	2
21	2
22	1
23	0
24	6
25	0
26	1
27	0
28	5
29	0
30	4
31	0
32	0
33	9
34	8
35	7
36	6
37	0
38	5
39	4
40	3
41	0
42	5
43	0
44	2
45	-1
46	1
47	0
48	-1
49	0
50	-1
51	6
52	5
53	0
54	4
55	-1
56	-1
57	2
58	1
59	0
60	-1
61	0
62	4
63	3
64	0
65	3
66	2
67	0
68	-1
69	-1
70	-1
71	0
72	-1
73	0

n	a(n)
1	0
2	0
3	0
4	0
5	0
6	1
7	0
8	0
9	0
10	1
11	0
12	3
13	0
14	2
15	1
16	0
17	0
18	3
19	0
20	2
21	2
22	1
23	0
24	6
25	0
26	1
27	0
28	5
29	0
30	4
31	0
32	0
33	9
34	8
35	7
36	6
37	0
38	5
39	4
40	3
41	0
42	5
43	0
44	2
45	-1
46	1
47	0
48	-1
49	0
50	-1
51	6
52	5
53	0
54	4
55	-1
56	-1
57	2
58	1
59	0
60	-1
61	0
62	4
63	3
64	0
65	3
66	2
67	0
68	-1
69	-1
70	-1
71	0
72	-1
73	0