A379727 - cp's OEIS frontend

A379727 a(1) = 1. For n > 1, a(n) = smallest prime factor of c=2a(n-1)+1 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 2c+1; and so on.

n	a(n)
1	1
2	3
3	7
4	5
5	11
6	23
7	47
8	19
9	13
10	37
11	151
12	101
13	29
14	59
15	17
16	71
17	41
18	83
19	167
20	67
21	271
22	181
23	727
24	97
25	1567
26	6271
27	113
28	227
29	911
30	1823
31	521
32	149
33	599
34	109
35	73
36	197
37	79
38	53
39	107
40	43
41	563
42	347
43	139
44	31
45	127
46	89
47	179
48	359
49	719
50	1439
51	2879
52	443
53	887
54	7103
55	14207
56	5683
57	421
58	281
59	1289
60	2579
61	607
62	1621
63	499
64	1999
65	5333
66	10667
67	251
68	503
69	733
70	163
71	131
72	263
73	211
74	3391
75	13567
76	7753
77	1723
78	383
79	307
80	1231
81	821
82	173
83	293

[1, 3, 7, 5, 11, 23, 47, 19, 13, 37, 151, 101, 29, 59, 17, 71, 41, 83, 167, 67, 271, 181, 727, 97, 1567, 6271, 113, 227, 911, 1823, 521, 149, 599, 109, 73, 197, 79, 53, 107, 43, 563, 347, 139, 31, 127, 89, 179, 359, 719, 1439, 2879, 443, 887, 7103, 14207, 5683, 421, 281, 1289, 2579, 607, 1621, 499, 1999, 5333, 10667, 251, 503, 733, 163, 131, 263, 211, 3391, 13567, 7753, 1723, 383, 307, 1231, 821, 173, 293]

cp's OEIS Frontend

A379727 a(1) = 1. For n > 1, a(n) = smallest prime factor of c=2a(n-1)+1 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 2c+1; and so on.

Table of values

List of values

cp's OEIS Frontend

A379727 a(1) = 1. For n > 1, a(n) = smallest prime factor of c=2*a(n-1)+1 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 2*c+1; and so on.

Table of values

List of values

A379727 a(1) = 1. For n > 1, a(n) = smallest prime factor of c=2a(n-1)+1 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 2c+1; and so on.