A133950 - cp's OEIS frontend

A133950 a(n) = the number of "isolated divisors" of n(n+1)/2. A positive divisor k of n is isolated if neither k-1 nor k+1 divides n.

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

[1, 2, 1, 2, 4, 4, 4, 5, 6, 4, 5, 5, 4, 8, 10, 6, 6, 6, 6, 8, 8, 4, 8, 12, 6, 8, 11, 6, 8, 8, 8, 14, 8, 8, 14, 9, 4, 8, 16, 8, 8, 8, 6, 16, 12, 4, 12, 17, 9, 12, 13, 6, 8, 16, 18, 18, 8, 4, 11, 11, 4, 12, 28, 20, 16, 8, 6, 13, 16, 8, 14, 14, 4, 12, 19, 14, 16, 8, 12, 31, 10, 4, 11, 22, 8, 8, 18]

cp's OEIS Frontend

A133950 a(n) = the number of "isolated divisors" of n(n+1)/2. A positive divisor k of n is isolated if neither k-1 nor k+1 divides n.

Table of values

List of values

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

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

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