A123246 - cp's OEIS frontend

A123246 a(n) = PrimePi(n) + (-1)^(PrimePi(n) + 1) (cf. A000720).

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

[-1, 2, 1, 1, 4, 4, 3, 3, 3, 3, 6, 6, 5, 5, 5, 5, 8, 8, 7, 7, 7, 7, 10, 10, 10, 10, 10, 10, 9, 9, 12, 12, 12, 12, 12, 12, 11, 11, 11, 11, 14, 14, 13, 13, 13, 13, 16, 16, 16, 16, 16, 16, 15, 15, 15, 15, 15, 15, 18, 18, 17, 17, 17, 17, 17, 17, 20, 20, 20, 20, 19, 19, 22, 22, 22, 22, 22, 22, 21, 21, 21, 21, 24, 24, 24, 24, 24, 24, 23, 23, 23, 23]

cp's OEIS Frontend

A123246 a(n) = PrimePi(n) + (-1)^(PrimePi(n) + 1) (cf. A000720).

Table of values

List of values

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

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

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