A251413 - cp's OEIS frontend

A251413 a(n) = 2n-1 if n <= 3, otherwise the smallest odd number not occurring earlier having at least one common factor with a(n-2), but none with a(n-1).

n	a(n)
1	1
2	3
3	5
4	9
5	25
6	21
7	55
8	7
9	11
10	35
11	33
12	49
13	15
14	77
15	27
16	91
17	45
18	13
19	51
20	65
21	17
22	39
23	85
24	57
25	115
26	19
27	23
28	95
29	69
30	125
31	63
32	145
33	81
34	29
35	75
36	203
37	93
38	119
39	31
40	105
41	341
42	87
43	121
44	111
45	143
46	37
47	99
48	185
49	117
50	155
51	123
52	175
53	41
54	133
55	205
56	147
57	215
58	141
59	43
60	47
61	129

[1, 3, 5, 9, 25, 21, 55, 7, 11, 35, 33, 49, 15, 77, 27, 91, 45, 13, 51, 65, 17, 39, 85, 57, 115, 19, 23, 95, 69, 125, 63, 145, 81, 29, 75, 203, 93, 119, 31, 105, 341, 87, 121, 111, 143, 37, 99, 185, 117, 155, 123, 175, 41, 133, 205, 147, 215, 141, 43, 47, 129]

cp's OEIS Frontend

A251413 a(n) = 2n-1 if n <= 3, otherwise the smallest odd number not occurring earlier having at least one common factor with a(n-2), but none with a(n-1).

Table of values

List of values

n	a(n)
1	1
2	3
3	5
4	9
5	25
6	21
7	55
8	7
9	11
10	35
11	33
12	49
13	15
14	77
15	27
16	91
17	45
18	13
19	51
20	65
21	17
22	39
23	85
24	57
25	115
26	19
27	23
28	95
29	69
30	125
31	63
32	145
33	81
34	29
35	75
36	203
37	93
38	119
39	31
40	105
41	341
42	87
43	121
44	111
45	143
46	37
47	99
48	185
49	117
50	155
51	123
52	175
53	41
54	133
55	205
56	147
57	215
58	141
59	43
60	47
61	129

n	a(n)
1	1
2	3
3	5
4	9
5	25
6	21
7	55
8	7
9	11
10	35
11	33
12	49
13	15
14	77
15	27
16	91
17	45
18	13
19	51
20	65
21	17
22	39
23	85
24	57
25	115
26	19
27	23
28	95
29	69
30	125
31	63
32	145
33	81
34	29
35	75
36	203
37	93
38	119
39	31
40	105
41	341
42	87
43	121
44	111
45	143
46	37
47	99
48	185
49	117
50	155
51	123
52	175
53	41
54	133
55	205
56	147
57	215
58	141
59	43
60	47
61	129

n	a(n)
1	1
2	3
3	5
4	9
5	25
6	21
7	55
8	7
9	11
10	35
11	33
12	49
13	15
14	77
15	27
16	91
17	45
18	13
19	51
20	65
21	17
22	39
23	85
24	57
25	115
26	19
27	23
28	95
29	69
30	125
31	63
32	145
33	81
34	29
35	75
36	203
37	93
38	119
39	31
40	105
41	341
42	87
43	121
44	111
45	143
46	37
47	99
48	185
49	117
50	155
51	123
52	175
53	41
54	133
55	205
56	147
57	215
58	141
59	43
60	47
61	129