A220693 - cp's OEIS frontend

A220693 Irregular triangle where the k-th item in the n-th row (both starting from 1) tells in how many ways we can add 2 distinct integers from 1 to n in such a way that the sum is divisible by k. Row n has 2n-1 terms.

n	a(n)
1	0
2	1
3	0
4	1
5	3
6	1
7	1
8	1
9	1
10	6
11	2
12	2
13	1
14	2
15	1
16	1
17	10
18	4
19	4
20	2
21	2
22	2
23	2
24	1
25	1
26	15
27	6
28	5
29	3
30	3
31	2
32	3
33	2
34	2
35	1
36	1
37	21
38	9
39	7
40	5
41	4
42	3
43	3
44	3
45	3
46	2
47	2
48	1
49	1
50	28
51	12
52	10
53	6
54	6
55	4
56	4
57	3
58	4
59	3
60	3
61	2
62	2
63	1
64	1
65	36
66	16
67	12
68	8
69	8
70	5
71	5
72	4
73	4
74	4
75	4
76	3
77	3
78	2
79	2
80	1
81	1

[0, 1, 0, 1, 3, 1, 1, 1, 1, 6, 2, 2, 1, 2, 1, 1, 10, 4, 4, 2, 2, 2, 2, 1, 1, 15, 6, 5, 3, 3, 2, 3, 2, 2, 1, 1, 21, 9, 7, 5, 4, 3, 3, 3, 3, 2, 2, 1, 1, 28, 12, 10, 6, 6, 4, 4, 3, 4, 3, 3, 2, 2, 1, 1, 36, 16, 12, 8, 8, 5, 5, 4, 4, 4, 4, 3, 3, 2, 2, 1, 1]

cp's OEIS Frontend

A220693 Irregular triangle where the k-th item in the n-th row (both starting from 1) tells in how many ways we can add 2 distinct integers from 1 to n in such a way that the sum is divisible by k. Row n has 2n-1 terms.

Table of values

List of values

n	a(n)
1	0
2	1
3	0
4	1
5	3
6	1
7	1
8	1
9	1
10	6
11	2
12	2
13	1
14	2
15	1
16	1
17	10
18	4
19	4
20	2
21	2
22	2
23	2
24	1
25	1
26	15
27	6
28	5
29	3
30	3
31	2
32	3
33	2
34	2
35	1
36	1
37	21
38	9
39	7
40	5
41	4
42	3
43	3
44	3
45	3
46	2
47	2
48	1
49	1
50	28
51	12
52	10
53	6
54	6
55	4
56	4
57	3
58	4
59	3
60	3
61	2
62	2
63	1
64	1
65	36
66	16
67	12
68	8
69	8
70	5
71	5
72	4
73	4
74	4
75	4
76	3
77	3
78	2
79	2
80	1
81	1

n	a(n)
1	0
2	1
3	0
4	1
5	3
6	1
7	1
8	1
9	1
10	6
11	2
12	2
13	1
14	2
15	1
16	1
17	10
18	4
19	4
20	2
21	2
22	2
23	2
24	1
25	1
26	15
27	6
28	5
29	3
30	3
31	2
32	3
33	2
34	2
35	1
36	1
37	21
38	9
39	7
40	5
41	4
42	3
43	3
44	3
45	3
46	2
47	2
48	1
49	1
50	28
51	12
52	10
53	6
54	6
55	4
56	4
57	3
58	4
59	3
60	3
61	2
62	2
63	1
64	1
65	36
66	16
67	12
68	8
69	8
70	5
71	5
72	4
73	4
74	4
75	4
76	3
77	3
78	2
79	2
80	1
81	1

n	a(n)
1	0
2	1
3	0
4	1
5	3
6	1
7	1
8	1
9	1
10	6
11	2
12	2
13	1
14	2
15	1
16	1
17	10
18	4
19	4
20	2
21	2
22	2
23	2
24	1
25	1
26	15
27	6
28	5
29	3
30	3
31	2
32	3
33	2
34	2
35	1
36	1
37	21
38	9
39	7
40	5
41	4
42	3
43	3
44	3
45	3
46	2
47	2
48	1
49	1
50	28
51	12
52	10
53	6
54	6
55	4
56	4
57	3
58	4
59	3
60	3
61	2
62	2
63	1
64	1
65	36
66	16
67	12
68	8
69	8
70	5
71	5
72	4
73	4
74	4
75	4
76	3
77	3
78	2
79	2
80	1
81	1