A360931 - cp's OEIS frontend

A360931 a(1) = 2, a(2) = 3; for n > 2, a(n) is the smallest number greater than 1 that has not appeared such that |a(n) - a(n-1)| has a common factor with a(n-2).

n	a(n)
1	2
2	3
3	5
4	8
5	13
6	7
7	20
8	6
9	4
10	10
11	12
12	14
13	11
14	9
15	31
16	16
17	47
18	15
19	62
20	17
21	19
22	36
23	55
24	21
25	26
26	23
27	25
28	48
29	18
30	22
31	24
32	28
33	30
34	32
35	27
36	29
37	35
38	64
39	34
40	38
41	40
42	42
43	37
44	33
45	70
46	43
47	39
48	82
49	46
50	44
51	50
52	52
53	54
54	41
55	45
56	86
57	51
58	49
59	58
60	65
61	53
62	63
63	116
64	56
65	60
66	66
67	57
68	59
69	68
70	127
71	61
72	188
73	249
74	67
75	73
76	140

[2, 3, 5, 8, 13, 7, 20, 6, 4, 10, 12, 14, 11, 9, 31, 16, 47, 15, 62, 17, 19, 36, 55, 21, 26, 23, 25, 48, 18, 22, 24, 28, 30, 32, 27, 29, 35, 64, 34, 38, 40, 42, 37, 33, 70, 43, 39, 82, 46, 44, 50, 52, 54, 41, 45, 86, 51, 49, 58, 65, 53, 63, 116, 56, 60, 66, 57, 59, 68, 127, 61, 188, 249, 67, 73, 140]

cp's OEIS Frontend

A360931 a(1) = 2, a(2) = 3; for n > 2, a(n) is the smallest number greater than 1 that has not appeared such that |a(n) - a(n-1)| has a common factor with a(n-2).

Table of values

List of values

n	a(n)
1	2
2	3
3	5
4	8
5	13
6	7
7	20
8	6
9	4
10	10
11	12
12	14
13	11
14	9
15	31
16	16
17	47
18	15
19	62
20	17
21	19
22	36
23	55
24	21
25	26
26	23
27	25
28	48
29	18
30	22
31	24
32	28
33	30
34	32
35	27
36	29
37	35
38	64
39	34
40	38
41	40
42	42
43	37
44	33
45	70
46	43
47	39
48	82
49	46
50	44
51	50
52	52
53	54
54	41
55	45
56	86
57	51
58	49
59	58
60	65
61	53
62	63
63	116
64	56
65	60
66	66
67	57
68	59
69	68
70	127
71	61
72	188
73	249
74	67
75	73
76	140

n	a(n)
1	2
2	3
3	5
4	8
5	13
6	7
7	20
8	6
9	4
10	10
11	12
12	14
13	11
14	9
15	31
16	16
17	47
18	15
19	62
20	17
21	19
22	36
23	55
24	21
25	26
26	23
27	25
28	48
29	18
30	22
31	24
32	28
33	30
34	32
35	27
36	29
37	35
38	64
39	34
40	38
41	40
42	42
43	37
44	33
45	70
46	43
47	39
48	82
49	46
50	44
51	50
52	52
53	54
54	41
55	45
56	86
57	51
58	49
59	58
60	65
61	53
62	63
63	116
64	56
65	60
66	66
67	57
68	59
69	68
70	127
71	61
72	188
73	249
74	67
75	73
76	140

n	a(n)
1	2
2	3
3	5
4	8
5	13
6	7
7	20
8	6
9	4
10	10
11	12
12	14
13	11
14	9
15	31
16	16
17	47
18	15
19	62
20	17
21	19
22	36
23	55
24	21
25	26
26	23
27	25
28	48
29	18
30	22
31	24
32	28
33	30
34	32
35	27
36	29
37	35
38	64
39	34
40	38
41	40
42	42
43	37
44	33
45	70
46	43
47	39
48	82
49	46
50	44
51	50
52	52
53	54
54	41
55	45
56	86
57	51
58	49
59	58
60	65
61	53
62	63
63	116
64	56
65	60
66	66
67	57
68	59
69	68
70	127
71	61
72	188
73	249
74	67
75	73
76	140