A239884 - cp's OEIS frontend

A239884 Least positive integer k <= n with pi(pi(k*n)) a square, or 0 if such a number k does not exist, where pi(x) denotes the number of primes not exceeding x.

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

[1, 1, 1, 1, 4, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 6, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 3, 3, 3, 3, 7, 7, 7, 13, 6, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 5, 16, 9, 9, 9, 9, 4, 4, 4, 4, 4, 4, 4, 4, 4, 13, 70, 20, 7, 7, 7, 7, 7, 7, 63, 11]

cp's OEIS Frontend

A239884 Least positive integer k <= n with pi(pi(k*n)) a square, or 0 if such a number k does not exist, where pi(x) denotes the number of primes not exceeding x.

Table of values

List of values

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

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

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