A216538 - cp's OEIS frontend

A216538 Numbers n such that the n-th Lucas number is prime, but cannot be written in the form a^2 + 7*b^2.

n	a(n)
1	2
2	8
3	11
4	13
5	31
6	41
7	47
8	61
9	79
10	313
11	617
12	863
13	1097
14	4793
15	5851
16	7741
17	12251
18	13963
19	35449
20	36779
21	44507
22	89849
23	140057
24	148091
25	202667
26	387433
27	443609
28	574219
29	631181
30	651821

[2, 8, 11, 13, 31, 41, 47, 61, 79, 313, 617, 863, 1097, 4793, 5851, 7741, 12251, 13963, 35449, 36779, 44507, 89849, 140057, 148091, 202667, 387433, 443609, 574219, 631181, 651821]

cp's OEIS Frontend

A216538 Numbers n such that the n-th Lucas number is prime, but cannot be written in the form a^2 + 7*b^2.

Table of values

List of values