A344371 - cp's OEIS frontend

A344371 a(n) = Sum_{k=1..n} (-1)^(n-k) gcd(k,n).

n	a(n)
1	1
2	1
3	3
4	4
5	5
6	5
7	7
8	12
9	9
10	9
11	11
12	20
13	13
14	13
15	15
16	32
17	17
18	21
19	19
20	36
21	21
22	21
23	23
24	60
25	25
26	25
27	27
28	52
29	29
30	45
31	31
32	80
33	33
34	33
35	35
36	84
37	37
38	37
39	39
40	108
41	41
42	65
43	43
44	84
45	45
46	45
47	47
48	160
49	49
50	65
51	51
52	100
53	53
54	81
55	55
56	156
57	57
58	57
59	59
60	180
61	61
62	61
63	63
64	192
65	65
66	105

[1, 1, 3, 4, 5, 5, 7, 12, 9, 9, 11, 20, 13, 13, 15, 32, 17, 21, 19, 36, 21, 21, 23, 60, 25, 25, 27, 52, 29, 45, 31, 80, 33, 33, 35, 84, 37, 37, 39, 108, 41, 65, 43, 84, 45, 45, 47, 160, 49, 65, 51, 100, 53, 81, 55, 156, 57, 57, 59, 180, 61, 61, 63, 192, 65, 105]

cp's OEIS Frontend

A344371 a(n) = Sum_{k=1..n} (-1)^(n-k) gcd(k,n).

Table of values

List of values

n	a(n)
1	1
2	1
3	3
4	4
5	5
6	5
7	7
8	12
9	9
10	9
11	11
12	20
13	13
14	13
15	15
16	32
17	17
18	21
19	19
20	36
21	21
22	21
23	23
24	60
25	25
26	25
27	27
28	52
29	29
30	45
31	31
32	80
33	33
34	33
35	35
36	84
37	37
38	37
39	39
40	108
41	41
42	65
43	43
44	84
45	45
46	45
47	47
48	160
49	49
50	65
51	51
52	100
53	53
54	81
55	55
56	156
57	57
58	57
59	59
60	180
61	61
62	61
63	63
64	192
65	65
66	105

n	a(n)
1	1
2	1
3	3
4	4
5	5
6	5
7	7
8	12
9	9
10	9
11	11
12	20
13	13
14	13
15	15
16	32
17	17
18	21
19	19
20	36
21	21
22	21
23	23
24	60
25	25
26	25
27	27
28	52
29	29
30	45
31	31
32	80
33	33
34	33
35	35
36	84
37	37
38	37
39	39
40	108
41	41
42	65
43	43
44	84
45	45
46	45
47	47
48	160
49	49
50	65
51	51
52	100
53	53
54	81
55	55
56	156
57	57
58	57
59	59
60	180
61	61
62	61
63	63
64	192
65	65
66	105

n	a(n)
1	1
2	1
3	3
4	4
5	5
6	5
7	7
8	12
9	9
10	9
11	11
12	20
13	13
14	13
15	15
16	32
17	17
18	21
19	19
20	36
21	21
22	21
23	23
24	60
25	25
26	25
27	27
28	52
29	29
30	45
31	31
32	80
33	33
34	33
35	35
36	84
37	37
38	37
39	39
40	108
41	41
42	65
43	43
44	84
45	45
46	45
47	47
48	160
49	49
50	65
51	51
52	100
53	53
54	81
55	55
56	156
57	57
58	57
59	59
60	180
61	61
62	61
63	63
64	192
65	65
66	105