A326440 - cp's OEIS frontend

A326440 a(n) = 1 - tau(1) + tau(2) - tau(3) + ... + (-1)^n tau(n), where tau = A000005 is number of divisors.

n	a(n)
0	1
1	0
2	2
3	0
4	3
5	1
6	5
7	3
8	7
9	4
10	8
11	6
12	12
13	10
14	14
15	10
16	15
17	13
18	19
19	17
20	23
21	19
22	23
23	21
24	29
25	26
26	30
27	26
28	32
29	30
30	38
31	36
32	42
33	38
34	42
35	38
36	47
37	45
38	49
39	45
40	53
41	51
42	59
43	57
44	63
45	57
46	61
47	59
48	69
49	66
50	72
51	68
52	74
53	72
54	80
55	76
56	84
57	80
58	84
59	82
60	94
61	92
62	96
63	90
64	97
65	93
66	101
67	99

[1, 0, 2, 0, 3, 1, 5, 3, 7, 4, 8, 6, 12, 10, 14, 10, 15, 13, 19, 17, 23, 19, 23, 21, 29, 26, 30, 26, 32, 30, 38, 36, 42, 38, 42, 38, 47, 45, 49, 45, 53, 51, 59, 57, 63, 57, 61, 59, 69, 66, 72, 68, 74, 72, 80, 76, 84, 80, 84, 82, 94, 92, 96, 90, 97, 93, 101, 99]

cp's OEIS Frontend

A326440 a(n) = 1 - tau(1) + tau(2) - tau(3) + ... + (-1)^n tau(n), where tau = A000005 is number of divisors.

Table of values

List of values

n	a(n)
0	1
1	0
2	2
3	0
4	3
5	1
6	5
7	3
8	7
9	4
10	8
11	6
12	12
13	10
14	14
15	10
16	15
17	13
18	19
19	17
20	23
21	19
22	23
23	21
24	29
25	26
26	30
27	26
28	32
29	30
30	38
31	36
32	42
33	38
34	42
35	38
36	47
37	45
38	49
39	45
40	53
41	51
42	59
43	57
44	63
45	57
46	61
47	59
48	69
49	66
50	72
51	68
52	74
53	72
54	80
55	76
56	84
57	80
58	84
59	82
60	94
61	92
62	96
63	90
64	97
65	93
66	101
67	99

n	a(n)
0	1
1	0
2	2
3	0
4	3
5	1
6	5
7	3
8	7
9	4
10	8
11	6
12	12
13	10
14	14
15	10
16	15
17	13
18	19
19	17
20	23
21	19
22	23
23	21
24	29
25	26
26	30
27	26
28	32
29	30
30	38
31	36
32	42
33	38
34	42
35	38
36	47
37	45
38	49
39	45
40	53
41	51
42	59
43	57
44	63
45	57
46	61
47	59
48	69
49	66
50	72
51	68
52	74
53	72
54	80
55	76
56	84
57	80
58	84
59	82
60	94
61	92
62	96
63	90
64	97
65	93
66	101
67	99

n	a(n)
0	1
1	0
2	2
3	0
4	3
5	1
6	5
7	3
8	7
9	4
10	8
11	6
12	12
13	10
14	14
15	10
16	15
17	13
18	19
19	17
20	23
21	19
22	23
23	21
24	29
25	26
26	30
27	26
28	32
29	30
30	38
31	36
32	42
33	38
34	42
35	38
36	47
37	45
38	49
39	45
40	53
41	51
42	59
43	57
44	63
45	57
46	61
47	59
48	69
49	66
50	72
51	68
52	74
53	72
54	80
55	76
56	84
57	80
58	84
59	82
60	94
61	92
62	96
63	90
64	97
65	93
66	101
67	99