A218459 - cp's OEIS frontend

A218459 a(n) is the smallest positive integer d such that prime(n) = x^2 + dy^2 has a solution (x,y) in integers.

n	a(n)
1	1
2	2
3	1
4	3
5	2
6	1
7	1
8	2
9	7
10	1
11	3
12	1
13	1
14	2
15	11
16	1
17	2
18	1
19	2
20	7
21	1
22	3
23	2
24	1
25	1
26	1
27	3
28	2
29	1
30	1
31	3
32	2
33	1
34	2
35	1
36	3
37	1
38	2
39	23
40	1
41	2
42	1
43	7
44	1
45	1
46	3
47	2
48	3
49	2
50	1
51	1
52	7
53	1
54	2
55	1
56	7
57	1
58	3
59	1
60	1
61	2
62	1
63	2
64	11
65	1
66	1
67	2
68	1
69	2
70	1
71	1
72	7
73	3
74	1
75	2
76	22
77	1
78	1
79	1
80	1
81	2
82	1
83	7
84	1
85	3
86	2
87	1
88	1
89	1
90	3
91	2
92	19
93	3
94	2
95	2

[1, 2, 1, 3, 2, 1, 1, 2, 7, 1, 3, 1, 1, 2, 11, 1, 2, 1, 2, 7, 1, 3, 2, 1, 1, 1, 3, 2, 1, 1, 3, 2, 1, 2, 1, 3, 1, 2, 23, 1, 2, 1, 7, 1, 1, 3, 2, 3, 2, 1, 1, 7, 1, 2, 1, 7, 1, 3, 1, 1, 2, 1, 2, 11, 1, 1, 2, 1, 2, 1, 1, 7, 3, 1, 2, 22, 1, 1, 1, 1, 2, 1, 7, 1, 3, 2, 1, 1, 1, 3, 2, 19, 3, 2, 2]

cp's OEIS Frontend

A218459 a(n) is the smallest positive integer d such that prime(n) = x^2 + dy^2 has a solution (x,y) in integers.

Table of values

List of values

n	a(n)
1	1
2	2
3	1
4	3
5	2
6	1
7	1
8	2
9	7
10	1
11	3
12	1
13	1
14	2
15	11
16	1
17	2
18	1
19	2
20	7
21	1
22	3
23	2
24	1
25	1
26	1
27	3
28	2
29	1
30	1
31	3
32	2
33	1
34	2
35	1
36	3
37	1
38	2
39	23
40	1
41	2
42	1
43	7
44	1
45	1
46	3
47	2
48	3
49	2
50	1
51	1
52	7
53	1
54	2
55	1
56	7
57	1
58	3
59	1
60	1
61	2
62	1
63	2
64	11
65	1
66	1
67	2
68	1
69	2
70	1
71	1
72	7
73	3
74	1
75	2
76	22
77	1
78	1
79	1
80	1
81	2
82	1
83	7
84	1
85	3
86	2
87	1
88	1
89	1
90	3
91	2
92	19
93	3
94	2
95	2

n	a(n)
1	1
2	2
3	1
4	3
5	2
6	1
7	1
8	2
9	7
10	1
11	3
12	1
13	1
14	2
15	11
16	1
17	2
18	1
19	2
20	7
21	1
22	3
23	2
24	1
25	1
26	1
27	3
28	2
29	1
30	1
31	3
32	2
33	1
34	2
35	1
36	3
37	1
38	2
39	23
40	1
41	2
42	1
43	7
44	1
45	1
46	3
47	2
48	3
49	2
50	1
51	1
52	7
53	1
54	2
55	1
56	7
57	1
58	3
59	1
60	1
61	2
62	1
63	2
64	11
65	1
66	1
67	2
68	1
69	2
70	1
71	1
72	7
73	3
74	1
75	2
76	22
77	1
78	1
79	1
80	1
81	2
82	1
83	7
84	1
85	3
86	2
87	1
88	1
89	1
90	3
91	2
92	19
93	3
94	2
95	2

n	a(n)
1	1
2	2
3	1
4	3
5	2
6	1
7	1
8	2
9	7
10	1
11	3
12	1
13	1
14	2
15	11
16	1
17	2
18	1
19	2
20	7
21	1
22	3
23	2
24	1
25	1
26	1
27	3
28	2
29	1
30	1
31	3
32	2
33	1
34	2
35	1
36	3
37	1
38	2
39	23
40	1
41	2
42	1
43	7
44	1
45	1
46	3
47	2
48	3
49	2
50	1
51	1
52	7
53	1
54	2
55	1
56	7
57	1
58	3
59	1
60	1
61	2
62	1
63	2
64	11
65	1
66	1
67	2
68	1
69	2
70	1
71	1
72	7
73	3
74	1
75	2
76	22
77	1
78	1
79	1
80	1
81	2
82	1
83	7
84	1
85	3
86	2
87	1
88	1
89	1
90	3
91	2
92	19
93	3
94	2
95	2