A275866 - cp's OEIS frontend

A275866 Number of semiprimes in {n, f(n), f(f(n)), ...., 1}, where f is the Collatz function.

n	a(n)
1	0
2	0
3	2
4	1
5	1
6	3
7	5
8	1
9	7
10	2
11	4
12	3
13	2
14	6
15	6
16	1
17	3
18	7
19	6
20	2
21	2
22	5
23	4
24	3
25	8
26	3
27	38
28	6
29	5
30	6
31	36
32	1
33	9
34	4
35	4
36	7
37	6
38	7
39	12
40	2
41	37
42	2
43	9
44	5
45	4
46	5
47	35
48	3
49	8
50	8
51	8
52	3
53	2
54	38
55	38
56	6
57	11
58	6
59	10
60	6
61	5
62	37
63	36
64	1
65	9
66	9
67	8
68	4
69	4
70	4
71	34
72	7
73	38
74	7
75	3
76	7
77	7
78	12
79	11
80	2
81	6
82	38

[0, 0, 2, 1, 1, 3, 5, 1, 7, 2, 4, 3, 2, 6, 6, 1, 3, 7, 6, 2, 2, 5, 4, 3, 8, 3, 38, 6, 5, 6, 36, 1, 9, 4, 4, 7, 6, 7, 12, 2, 37, 2, 9, 5, 4, 5, 35, 3, 8, 8, 8, 3, 2, 38, 38, 6, 11, 6, 10, 6, 5, 37, 36, 1, 9, 9, 8, 4, 4, 4, 34, 7, 38, 7, 3, 7, 7, 12, 11, 2, 6, 38]

cp's OEIS Frontend

A275866 Number of semiprimes in {n, f(n), f(f(n)), ...., 1}, where f is the Collatz function.

Table of values

List of values

n	a(n)
1	0
2	0
3	2
4	1
5	1
6	3
7	5
8	1
9	7
10	2
11	4
12	3
13	2
14	6
15	6
16	1
17	3
18	7
19	6
20	2
21	2
22	5
23	4
24	3
25	8
26	3
27	38
28	6
29	5
30	6
31	36
32	1
33	9
34	4
35	4
36	7
37	6
38	7
39	12
40	2
41	37
42	2
43	9
44	5
45	4
46	5
47	35
48	3
49	8
50	8
51	8
52	3
53	2
54	38
55	38
56	6
57	11
58	6
59	10
60	6
61	5
62	37
63	36
64	1
65	9
66	9
67	8
68	4
69	4
70	4
71	34
72	7
73	38
74	7
75	3
76	7
77	7
78	12
79	11
80	2
81	6
82	38

n	a(n)
1	0
2	0
3	2
4	1
5	1
6	3
7	5
8	1
9	7
10	2
11	4
12	3
13	2
14	6
15	6
16	1
17	3
18	7
19	6
20	2
21	2
22	5
23	4
24	3
25	8
26	3
27	38
28	6
29	5
30	6
31	36
32	1
33	9
34	4
35	4
36	7
37	6
38	7
39	12
40	2
41	37
42	2
43	9
44	5
45	4
46	5
47	35
48	3
49	8
50	8
51	8
52	3
53	2
54	38
55	38
56	6
57	11
58	6
59	10
60	6
61	5
62	37
63	36
64	1
65	9
66	9
67	8
68	4
69	4
70	4
71	34
72	7
73	38
74	7
75	3
76	7
77	7
78	12
79	11
80	2
81	6
82	38

n	a(n)
1	0
2	0
3	2
4	1
5	1
6	3
7	5
8	1
9	7
10	2
11	4
12	3
13	2
14	6
15	6
16	1
17	3
18	7
19	6
20	2
21	2
22	5
23	4
24	3
25	8
26	3
27	38
28	6
29	5
30	6
31	36
32	1
33	9
34	4
35	4
36	7
37	6
38	7
39	12
40	2
41	37
42	2
43	9
44	5
45	4
46	5
47	35
48	3
49	8
50	8
51	8
52	3
53	2
54	38
55	38
56	6
57	11
58	6
59	10
60	6
61	5
62	37
63	36
64	1
65	9
66	9
67	8
68	4
69	4
70	4
71	34
72	7
73	38
74	7
75	3
76	7
77	7
78	12
79	11
80	2
81	6
82	38