A221956 - cp's OEIS frontend

A221956 Number of values in the Collatz (3x+1) trajectory starting at n that are also present in the trajectory for some k < n.

n	a(n)
1	0
2	1
3	2
4	3
5	6
6	8
7	7
8	4
9	17
10	7
11	15
12	9
13	10
14	18
15	9
16	5
17	13
18	20
19	16
20	8
21	5
22	16
23	16
24	10
25	21
26	11
27	17
28	19
29	19
30	18
31	107
32	6
33	24
34	14
35	14
36	21
37	19
38	22
39	23
40	9
41	110
42	8
43	22
44	17
45	14
46	17
47	105
48	11
49	25
50	25
51	20
52	12
53	12
54	112
55	106
56	20
57	30
58	20
59	33
60	19
61	20
62	108
63	95
64	7
65	28
66	27
67	28
68	15
69	12

[0, 1, 2, 3, 6, 8, 7, 4, 17, 7, 15, 9, 10, 18, 9, 5, 13, 20, 16, 8, 5, 16, 16, 10, 21, 11, 17, 19, 19, 18, 107, 6, 24, 14, 14, 21, 19, 22, 23, 9, 110, 8, 22, 17, 14, 17, 105, 11, 25, 25, 20, 12, 12, 112, 106, 20, 30, 20, 33, 19, 20, 108, 95, 7, 28, 27, 28, 15, 12]

cp's OEIS Frontend

A221956 Number of values in the Collatz (3x+1) trajectory starting at n that are also present in the trajectory for some k < n.

Table of values

List of values

n	a(n)
1	0
2	1
3	2
4	3
5	6
6	8
7	7
8	4
9	17
10	7
11	15
12	9
13	10
14	18
15	9
16	5
17	13
18	20
19	16
20	8
21	5
22	16
23	16
24	10
25	21
26	11
27	17
28	19
29	19
30	18
31	107
32	6
33	24
34	14
35	14
36	21
37	19
38	22
39	23
40	9
41	110
42	8
43	22
44	17
45	14
46	17
47	105
48	11
49	25
50	25
51	20
52	12
53	12
54	112
55	106
56	20
57	30
58	20
59	33
60	19
61	20
62	108
63	95
64	7
65	28
66	27
67	28
68	15
69	12

n	a(n)
1	0
2	1
3	2
4	3
5	6
6	8
7	7
8	4
9	17
10	7
11	15
12	9
13	10
14	18
15	9
16	5
17	13
18	20
19	16
20	8
21	5
22	16
23	16
24	10
25	21
26	11
27	17
28	19
29	19
30	18
31	107
32	6
33	24
34	14
35	14
36	21
37	19
38	22
39	23
40	9
41	110
42	8
43	22
44	17
45	14
46	17
47	105
48	11
49	25
50	25
51	20
52	12
53	12
54	112
55	106
56	20
57	30
58	20
59	33
60	19
61	20
62	108
63	95
64	7
65	28
66	27
67	28
68	15
69	12

n	a(n)
1	0
2	1
3	2
4	3
5	6
6	8
7	7
8	4
9	17
10	7
11	15
12	9
13	10
14	18
15	9
16	5
17	13
18	20
19	16
20	8
21	5
22	16
23	16
24	10
25	21
26	11
27	17
28	19
29	19
30	18
31	107
32	6
33	24
34	14
35	14
36	21
37	19
38	22
39	23
40	9
41	110
42	8
43	22
44	17
45	14
46	17
47	105
48	11
49	25
50	25
51	20
52	12
53	12
54	112
55	106
56	20
57	30
58	20
59	33
60	19
61	20
62	108
63	95
64	7
65	28
66	27
67	28
68	15
69	12