A380288 - cp's OEIS frontend

A380288 a(n) is the number of divisors d of n such that 2^d - 1 is not prime.

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

[1, 1, 1, 2, 1, 2, 1, 3, 2, 2, 2, 4, 1, 2, 2, 4, 1, 4, 1, 4, 2, 3, 2, 6, 2, 2, 3, 4, 2, 5, 1, 5, 3, 2, 2, 7, 2, 2, 2, 6, 2, 5, 2, 5, 4, 3, 2, 8, 2, 4, 2, 4, 2, 6, 3, 6, 2, 3, 2, 9, 1, 2, 4, 6, 2, 6, 2, 4, 3, 5, 2, 10, 2, 3, 4, 4, 3, 5, 2, 8, 4, 3, 2, 9, 2, 3, 3, 7, 1, 9, 2, 5, 2, 3, 2, 10, 2, 4, 5, 7]

cp's OEIS Frontend

A380288 a(n) is the number of divisors d of n such that 2^d - 1 is not prime.

Table of values

List of values

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

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

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