A077140 - cp's OEIS frontend

A077140 a(1) = 1 and then add n to the previous term if n is coprime to the previous term, otherwise subtract n from the previous term. a(1) = 1 and a(n) = a(n-1) + n if gcd(n, a(n-1)) = 1, otherwise a(n) = a(n-1) - n.

n	a(n)
1	1
2	3
3	0
4	-4
5	1
6	7
7	0
8	-8
9	1
10	11
11	0
12	-12
13	1
14	15
15	0
16	-16
17	1
18	19
19	0
20	-20
21	1
22	23
23	0
24	-24
25	1
26	27
27	0
28	-28
29	1
30	31
31	0
32	-32
33	1
34	35
35	0
36	-36
37	1
38	39
39	0
40	-40
41	1
42	43
43	0
44	-44
45	1
46	47
47	0
48	-48
49	1
50	51
51	0
52	-52
53	1
54	55
55	0

[1, 3, 0, -4, 1, 7, 0, -8, 1, 11, 0, -12, 1, 15, 0, -16, 1, 19, 0, -20, 1, 23, 0, -24, 1, 27, 0, -28, 1, 31, 0, -32, 1, 35, 0, -36, 1, 39, 0, -40, 1, 43, 0, -44, 1, 47, 0, -48, 1, 51, 0, -52, 1, 55, 0]

cp's OEIS Frontend

A077140 a(1) = 1 and then add n to the previous term if n is coprime to the previous term, otherwise subtract n from the previous term. a(1) = 1 and a(n) = a(n-1) + n if gcd(n, a(n-1)) = 1, otherwise a(n) = a(n-1) - n.

Table of values

List of values

n	a(n)
1	1
2	3
3	0
4	-4
5	1
6	7
7	0
8	-8
9	1
10	11
11	0
12	-12
13	1
14	15
15	0
16	-16
17	1
18	19
19	0
20	-20
21	1
22	23
23	0
24	-24
25	1
26	27
27	0
28	-28
29	1
30	31
31	0
32	-32
33	1
34	35
35	0
36	-36
37	1
38	39
39	0
40	-40
41	1
42	43
43	0
44	-44
45	1
46	47
47	0
48	-48
49	1
50	51
51	0
52	-52
53	1
54	55
55	0

n	a(n)
1	1
2	3
3	0
4	-4
5	1
6	7
7	0
8	-8
9	1
10	11
11	0
12	-12
13	1
14	15
15	0
16	-16
17	1
18	19
19	0
20	-20
21	1
22	23
23	0
24	-24
25	1
26	27
27	0
28	-28
29	1
30	31
31	0
32	-32
33	1
34	35
35	0
36	-36
37	1
38	39
39	0
40	-40
41	1
42	43
43	0
44	-44
45	1
46	47
47	0
48	-48
49	1
50	51
51	0
52	-52
53	1
54	55
55	0

n	a(n)
1	1
2	3
3	0
4	-4
5	1
6	7
7	0
8	-8
9	1
10	11
11	0
12	-12
13	1
14	15
15	0
16	-16
17	1
18	19
19	0
20	-20
21	1
22	23
23	0
24	-24
25	1
26	27
27	0
28	-28
29	1
30	31
31	0
32	-32
33	1
34	35
35	0
36	-36
37	1
38	39
39	0
40	-40
41	1
42	43
43	0
44	-44
45	1
46	47
47	0
48	-48
49	1
50	51
51	0
52	-52
53	1
54	55
55	0