A278572 - cp's OEIS frontend

A278572 Irregular triangle read by rows: row n lists values of k in range 1 <= k <= n/2 such x^n + x^k + 1 is irreducible (mod 2), or -1 if no such k exists.

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

[1, 1, 1, 2, 1, 3, 1, 3, -1, 1, 4, 3, 2, 3, 5, -1, 5, 1, 4, 7, -1, 3, 5, 6, 3, 7, 9, -1, 3, 5, 2, 7, 1, 5, 9, -1, 3, 7, -1, -1, 1, 3, 9, 13, 2, 1, 9, 3, 6, 7, 13, -1, 10, 13, 7, 2, 9, 11, 15, -1, -1, 4, 8, 14, -1, 3, 20, 7, -1, 5, -1, 1, 5, 14, 20, 21, -1]

cp's OEIS Frontend

A278572 Irregular triangle read by rows: row n lists values of k in range 1 <= k <= n/2 such x^n + x^k + 1 is irreducible (mod 2), or -1 if no such k exists.

Table of values

List of values

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

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

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