A379899 - cp's OEIS frontend

A379899 a(1) = 2. For n > 1, a(n) = smallest prime factor of c=a(n-1)+4 that is not in {a(1), ..., a(n-1)}; if all prime factors of c are in {a(1), ..., a(n-1)}, then we try the next value of c, which is c+4; and so on.

n	a(n)
1	2
2	3
3	7
4	11
5	5
6	13
7	17
8	29
9	37
10	41
11	53
12	19
13	23
14	31
15	43
16	47
17	59
18	67
19	71
20	79
21	83
22	103
23	107
24	127
25	131
26	139
27	151
28	163
29	167
30	179
31	61
32	73
33	89
34	97
35	101
36	109
37	113
38	137
39	149
40	157
41	173
42	181
43	193
44	197
45	229
46	233
47	241
48	257
49	269
50	277
51	281
52	293
53	313
54	317
55	337
56	349
57	353
58	373

[2, 3, 7, 11, 5, 13, 17, 29, 37, 41, 53, 19, 23, 31, 43, 47, 59, 67, 71, 79, 83, 103, 107, 127, 131, 139, 151, 163, 167, 179, 61, 73, 89, 97, 101, 109, 113, 137, 149, 157, 173, 181, 193, 197, 229, 233, 241, 257, 269, 277, 281, 293, 313, 317, 337, 349, 353, 373]

cp's OEIS Frontend

A379899 a(1) = 2. For n > 1, a(n) = smallest prime factor of c=a(n-1)+4 that is not in {a(1), ..., a(n-1)}; if all prime factors of c are in {a(1), ..., a(n-1)}, then we try the next value of c, which is c+4; and so on.

Table of values

List of values

n	a(n)
1	2
2	3
3	7
4	11
5	5
6	13
7	17
8	29
9	37
10	41
11	53
12	19
13	23
14	31
15	43
16	47
17	59
18	67
19	71
20	79
21	83
22	103
23	107
24	127
25	131
26	139
27	151
28	163
29	167
30	179
31	61
32	73
33	89
34	97
35	101
36	109
37	113
38	137
39	149
40	157
41	173
42	181
43	193
44	197
45	229
46	233
47	241
48	257
49	269
50	277
51	281
52	293
53	313
54	317
55	337
56	349
57	353
58	373

n	a(n)
1	2
2	3
3	7
4	11
5	5
6	13
7	17
8	29
9	37
10	41
11	53
12	19
13	23
14	31
15	43
16	47
17	59
18	67
19	71
20	79
21	83
22	103
23	107
24	127
25	131
26	139
27	151
28	163
29	167
30	179
31	61
32	73
33	89
34	97
35	101
36	109
37	113
38	137
39	149
40	157
41	173
42	181
43	193
44	197
45	229
46	233
47	241
48	257
49	269
50	277
51	281
52	293
53	313
54	317
55	337
56	349
57	353
58	373

n	a(n)
1	2
2	3
3	7
4	11
5	5
6	13
7	17
8	29
9	37
10	41
11	53
12	19
13	23
14	31
15	43
16	47
17	59
18	67
19	71
20	79
21	83
22	103
23	107
24	127
25	131
26	139
27	151
28	163
29	167
30	179
31	61
32	73
33	89
34	97
35	101
36	109
37	113
38	137
39	149
40	157
41	173
42	181
43	193
44	197
45	229
46	233
47	241
48	257
49	269
50	277
51	281
52	293
53	313
54	317
55	337
56	349
57	353
58	373