A081387 - cp's OEIS frontend

A081387 Number of non-unitary prime divisors of central binomial coefficient, C(2n,n) = A000984(n), i.e., number of prime factors in C(2n,n) whose exponent is greater than one.

n	a(n)
1	0
2	0
3	1
4	0
5	2
6	1
7	1
8	1
9	1
10	1
11	1
12	1
13	2
14	3
15	2
16	1
17	2
18	2
19	2
20	2
21	1
22	1
23	3
24	3
25	3
26	3
27	2
28	1
29	1
30	1
31	1
32	2
33	2
34	2
35	2
36	1
37	1
38	2
39	3
40	2
41	3
42	2
43	3
44	3
45	2
46	3
47	3
48	4
49	3
50	2
51	2
52	2
53	2
54	1
55	1
56	2
57	1
58	1
59	2
60	2
61	3
62	3
63	3
64	2
65	4
66	2
67	2
68	3
69	3
70	3
71	3
72	4
73	4
74	5
75	4
76	4
77	2
78	3
79	3
80	2
81	2
82	2
83	4
84	3
85	3
86	4
87	3
88	4
89	5
90	4
91	2
92	2
93	2
94	3
95	5
96	5
97	5
98	5
99	3
100	2
101	3
102	2
103	3
104	3
105	3

[0, 0, 1, 0, 2, 1, 1, 1, 1, 1, 1, 1, 2, 3, 2, 1, 2, 2, 2, 2, 1, 1, 3, 3, 3, 3, 2, 1, 1, 1, 1, 2, 2, 2, 2, 1, 1, 2, 3, 2, 3, 2, 3, 3, 2, 3, 3, 4, 3, 2, 2, 2, 2, 1, 1, 2, 1, 1, 2, 2, 3, 3, 3, 2, 4, 2, 2, 3, 3, 3, 3, 4, 4, 5, 4, 4, 2, 3, 3, 2, 2, 2, 4, 3, 3, 4, 3, 4, 5, 4, 2, 2, 2, 3, 5, 5, 5, 5, 3, 2, 3, 2, 3, 3, 3]

cp's OEIS Frontend

A081387 Number of non-unitary prime divisors of central binomial coefficient, C(2n,n) = A000984(n), i.e., number of prime factors in C(2n,n) whose exponent is greater than one.

Table of values

List of values

n	a(n)
1	0
2	0
3	1
4	0
5	2
6	1
7	1
8	1
9	1
10	1
11	1
12	1
13	2
14	3
15	2
16	1
17	2
18	2
19	2
20	2
21	1
22	1
23	3
24	3
25	3
26	3
27	2
28	1
29	1
30	1
31	1
32	2
33	2
34	2
35	2
36	1
37	1
38	2
39	3
40	2
41	3
42	2
43	3
44	3
45	2
46	3
47	3
48	4
49	3
50	2
51	2
52	2
53	2
54	1
55	1
56	2
57	1
58	1
59	2
60	2
61	3
62	3
63	3
64	2
65	4
66	2
67	2
68	3
69	3
70	3
71	3
72	4
73	4
74	5
75	4
76	4
77	2
78	3
79	3
80	2
81	2
82	2
83	4
84	3
85	3
86	4
87	3
88	4
89	5
90	4
91	2
92	2
93	2
94	3
95	5
96	5
97	5
98	5
99	3
100	2
101	3
102	2
103	3
104	3
105	3

n	a(n)
1	0
2	0
3	1
4	0
5	2
6	1
7	1
8	1
9	1
10	1
11	1
12	1
13	2
14	3
15	2
16	1
17	2
18	2
19	2
20	2
21	1
22	1
23	3
24	3
25	3
26	3
27	2
28	1
29	1
30	1
31	1
32	2
33	2
34	2
35	2
36	1
37	1
38	2
39	3
40	2
41	3
42	2
43	3
44	3
45	2
46	3
47	3
48	4
49	3
50	2
51	2
52	2
53	2
54	1
55	1
56	2
57	1
58	1
59	2
60	2
61	3
62	3
63	3
64	2
65	4
66	2
67	2
68	3
69	3
70	3
71	3
72	4
73	4
74	5
75	4
76	4
77	2
78	3
79	3
80	2
81	2
82	2
83	4
84	3
85	3
86	4
87	3
88	4
89	5
90	4
91	2
92	2
93	2
94	3
95	5
96	5
97	5
98	5
99	3
100	2
101	3
102	2
103	3
104	3
105	3

n	a(n)
1	0
2	0
3	1
4	0
5	2
6	1
7	1
8	1
9	1
10	1
11	1
12	1
13	2
14	3
15	2
16	1
17	2
18	2
19	2
20	2
21	1
22	1
23	3
24	3
25	3
26	3
27	2
28	1
29	1
30	1
31	1
32	2
33	2
34	2
35	2
36	1
37	1
38	2
39	3
40	2
41	3
42	2
43	3
44	3
45	2
46	3
47	3
48	4
49	3
50	2
51	2
52	2
53	2
54	1
55	1
56	2
57	1
58	1
59	2
60	2
61	3
62	3
63	3
64	2
65	4
66	2
67	2
68	3
69	3
70	3
71	3
72	4
73	4
74	5
75	4
76	4
77	2
78	3
79	3
80	2
81	2
82	2
83	4
84	3
85	3
86	4
87	3
88	4
89	5
90	4
91	2
92	2
93	2
94	3
95	5
96	5
97	5
98	5
99	3
100	2
101	3
102	2
103	3
104	3
105	3