A267097 - cp's OEIS frontend

A267097 a(n) = number of 4k+1 primes among first n primes; least monotonic left inverse of A080147.

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

[0, 0, 1, 1, 1, 2, 3, 3, 3, 4, 4, 5, 6, 6, 6, 7, 7, 8, 8, 8, 9, 9, 9, 10, 11, 12, 12, 12, 13, 14, 14, 14, 15, 15, 16, 16, 17, 17, 17, 18, 18, 19, 19, 20, 21, 21, 21, 21, 21, 22, 23, 23, 24, 24, 25, 25, 26, 26, 27, 28, 28, 29, 29, 29, 30, 31, 31, 32, 32, 33, 34, 34, 34, 35, 35, 35, 36, 37, 38, 39, 39, 40, 40, 41]

cp's OEIS Frontend

A267097 a(n) = number of 4k+1 primes among first n primes; least monotonic left inverse of A080147.

Table of values

List of values

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

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

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