A228446 - cp's OEIS frontend

A228446 a(n) = smallest prime p such that 2n+1 = p + x(x+1) for some positive integer x, or -1 if no such prime exists.

n	a(n)
2	3
3	5
4	3
5	5
6	7
7	3
8	5
9	7
10	19
11	3
12	5
13	7
14	17
15	11
16	3
17	5
18	7
19	19
20	11
21	13
22	3
23	5
24	7
25	31
26	11
27	13
28	37
29	3
30	5
31	7
32	23
33	11
34	13
35	29
36	17
37	3
38	5
39	7
40	61
41	11
42	13
43	31
44	17
45	19
46	3
47	5
48	7
49	43
50	11
51	13
52	103
53	17
54	19
55	109
56	3
57	5
58	7
59	29
60	11
61	13
62	53
63	17
64	19
65	41
66	23
67	3
68	5
69	7
70	31
71	11
72	13
73	37

[3, 5, 3, 5, 7, 3, 5, 7, 19, 3, 5, 7, 17, 11, 3, 5, 7, 19, 11, 13, 3, 5, 7, 31, 11, 13, 37, 3, 5, 7, 23, 11, 13, 29, 17, 3, 5, 7, 61, 11, 13, 31, 17, 19, 3, 5, 7, 43, 11, 13, 103, 17, 19, 109, 3, 5, 7, 29, 11, 13, 53, 17, 19, 41, 23, 3, 5, 7, 31, 11, 13, 37]

cp's OEIS Frontend

A228446 a(n) = smallest prime p such that 2n+1 = p + x(x+1) for some positive integer x, or -1 if no such prime exists.

Table of values

List of values

n	a(n)
2	3
3	5
4	3
5	5
6	7
7	3
8	5
9	7
10	19
11	3
12	5
13	7
14	17
15	11
16	3
17	5
18	7
19	19
20	11
21	13
22	3
23	5
24	7
25	31
26	11
27	13
28	37
29	3
30	5
31	7
32	23
33	11
34	13
35	29
36	17
37	3
38	5
39	7
40	61
41	11
42	13
43	31
44	17
45	19
46	3
47	5
48	7
49	43
50	11
51	13
52	103
53	17
54	19
55	109
56	3
57	5
58	7
59	29
60	11
61	13
62	53
63	17
64	19
65	41
66	23
67	3
68	5
69	7
70	31
71	11
72	13
73	37

n	a(n)
2	3
3	5
4	3
5	5
6	7
7	3
8	5
9	7
10	19
11	3
12	5
13	7
14	17
15	11
16	3
17	5
18	7
19	19
20	11
21	13
22	3
23	5
24	7
25	31
26	11
27	13
28	37
29	3
30	5
31	7
32	23
33	11
34	13
35	29
36	17
37	3
38	5
39	7
40	61
41	11
42	13
43	31
44	17
45	19
46	3
47	5
48	7
49	43
50	11
51	13
52	103
53	17
54	19
55	109
56	3
57	5
58	7
59	29
60	11
61	13
62	53
63	17
64	19
65	41
66	23
67	3
68	5
69	7
70	31
71	11
72	13
73	37

cp's OEIS Frontend

A228446 a(n) = smallest prime p such that 2*n+1 = p + x*(x+1) for some positive integer x, or -1 if no such prime exists.

Table of values

List of values

A228446 a(n) = smallest prime p such that 2n+1 = p + x(x+1) for some positive integer x, or -1 if no such prime exists.

n	a(n)
2	3
3	5
4	3
5	5
6	7
7	3
8	5
9	7
10	19
11	3
12	5
13	7
14	17
15	11
16	3
17	5
18	7
19	19
20	11
21	13
22	3
23	5
24	7
25	31
26	11
27	13
28	37
29	3
30	5
31	7
32	23
33	11
34	13
35	29
36	17
37	3
38	5
39	7
40	61
41	11
42	13
43	31
44	17
45	19
46	3
47	5
48	7
49	43
50	11
51	13
52	103
53	17
54	19
55	109
56	3
57	5
58	7
59	29
60	11
61	13
62	53
63	17
64	19
65	41
66	23
67	3
68	5
69	7
70	31
71	11
72	13
73	37