A271860 - cp's OEIS frontend

A271860 a(n) = -Sum_{i=1..n} (-1)^floor(n/i).

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

[0, 1, 0, 3, 0, 3, 2, 5, 0, 5, 4, 7, 2, 5, 4, 11, 4, 7, 6, 9, 4, 11, 10, 13, 4, 9, 8, 15, 10, 13, 12, 15, 6, 13, 12, 19, 12, 15, 14, 21, 12, 15, 14, 17, 12, 23, 22, 25, 12, 17, 16, 23, 18, 21, 20, 27, 18, 25, 24, 27, 18, 21, 20, 31, 20, 27, 26, 29, 24, 31, 30]

cp's OEIS Frontend

A271860 a(n) = -Sum_{i=1..n} (-1)^floor(n/i).

Table of values

List of values

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

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

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