A199084 - cp's OEIS frontend

A199084 a(n) = Sum_{k=1..n} (-1)^(k+1) 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

[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]

cp's OEIS Frontend

A199084 a(n) = Sum_{k=1..n} (-1)^(k+1) gcd(k,n).

Table of values

List of values