A056171 - cp's OEIS frontend

A056171 a(n) = pi(n) - pi(floor(n/2)), where pi is A000720.

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

[0, 1, 2, 1, 2, 1, 2, 2, 2, 1, 2, 2, 3, 2, 2, 2, 3, 3, 4, 4, 4, 3, 4, 4, 4, 3, 3, 3, 4, 4, 5, 5, 5, 4, 4, 4, 5, 4, 4, 4, 5, 5, 6, 6, 6, 5, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 6, 7, 7, 8, 7, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 10, 9, 9, 9, 9, 9, 10, 10, 10, 9, 10, 10, 10, 9, 9, 9, 10, 10, 10, 10, 10, 9, 9, 9, 10, 10]

cp's OEIS Frontend

A056171 a(n) = pi(n) - pi(floor(n/2)), where pi is A000720.

Table of values

List of values

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

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

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