A061857 - cp's OEIS frontend

A061857 Triangle in which the k-th item in the n-th row (both starting from 1) is the number of ways in which we can add 2 distinct integers from 1 to n in such a way that the sum is divisible by k.

n	a(n)
1	0
2	1
3	0
4	3
5	1
6	1
7	6
8	2
9	2
10	1
11	10
12	4
13	4
14	2
15	2
16	15
17	6
18	5
19	3
20	3
21	2
22	21
23	9
24	7
25	5
26	4
27	3
28	3
29	28
30	12
31	10
32	6
33	6
34	4
35	4
36	3
37	36
38	16
39	12
40	8
41	8
42	5
43	5
44	4
45	4
46	45
47	20
48	15
49	10
50	9
51	7
52	6
53	5
54	5
55	4
56	55
57	25
58	19
59	13
60	11
61	9
62	8
63	6
64	6
65	5
66	5
67	66
68	30
69	22
70	15
71	13
72	10
73	10
74	7
75	7
76	6
77	6
78	5
79	78
80	36
81	26
82	18
83	16
84	12
85	12
86	9
87	8
88	7
89	7

[0, 1, 0, 3, 1, 1, 6, 2, 2, 1, 10, 4, 4, 2, 2, 15, 6, 5, 3, 3, 2, 21, 9, 7, 5, 4, 3, 3, 28, 12, 10, 6, 6, 4, 4, 3, 36, 16, 12, 8, 8, 5, 5, 4, 4, 45, 20, 15, 10, 9, 7, 6, 5, 5, 4, 55, 25, 19, 13, 11, 9, 8, 6, 6, 5, 5, 66, 30, 22, 15, 13, 10, 10, 7, 7, 6, 6, 5, 78, 36, 26, 18, 16, 12, 12, 9, 8, 7, 7]

cp's OEIS Frontend

A061857 Triangle in which the k-th item in the n-th row (both starting from 1) is the number of ways in which we can add 2 distinct integers from 1 to n in such a way that the sum is divisible by k.

Table of values

List of values

n	a(n)
1	0
2	1
3	0
4	3
5	1
6	1
7	6
8	2
9	2
10	1
11	10
12	4
13	4
14	2
15	2
16	15
17	6
18	5
19	3
20	3
21	2
22	21
23	9
24	7
25	5
26	4
27	3
28	3
29	28
30	12
31	10
32	6
33	6
34	4
35	4
36	3
37	36
38	16
39	12
40	8
41	8
42	5
43	5
44	4
45	4
46	45
47	20
48	15
49	10
50	9
51	7
52	6
53	5
54	5
55	4
56	55
57	25
58	19
59	13
60	11
61	9
62	8
63	6
64	6
65	5
66	5
67	66
68	30
69	22
70	15
71	13
72	10
73	10
74	7
75	7
76	6
77	6
78	5
79	78
80	36
81	26
82	18
83	16
84	12
85	12
86	9
87	8
88	7
89	7

n	a(n)
1	0
2	1
3	0
4	3
5	1
6	1
7	6
8	2
9	2
10	1
11	10
12	4
13	4
14	2
15	2
16	15
17	6
18	5
19	3
20	3
21	2
22	21
23	9
24	7
25	5
26	4
27	3
28	3
29	28
30	12
31	10
32	6
33	6
34	4
35	4
36	3
37	36
38	16
39	12
40	8
41	8
42	5
43	5
44	4
45	4
46	45
47	20
48	15
49	10
50	9
51	7
52	6
53	5
54	5
55	4
56	55
57	25
58	19
59	13
60	11
61	9
62	8
63	6
64	6
65	5
66	5
67	66
68	30
69	22
70	15
71	13
72	10
73	10
74	7
75	7
76	6
77	6
78	5
79	78
80	36
81	26
82	18
83	16
84	12
85	12
86	9
87	8
88	7
89	7

n	a(n)
1	0
2	1
3	0
4	3
5	1
6	1
7	6
8	2
9	2
10	1
11	10
12	4
13	4
14	2
15	2
16	15
17	6
18	5
19	3
20	3
21	2
22	21
23	9
24	7
25	5
26	4
27	3
28	3
29	28
30	12
31	10
32	6
33	6
34	4
35	4
36	3
37	36
38	16
39	12
40	8
41	8
42	5
43	5
44	4
45	4
46	45
47	20
48	15
49	10
50	9
51	7
52	6
53	5
54	5
55	4
56	55
57	25
58	19
59	13
60	11
61	9
62	8
63	6
64	6
65	5
66	5
67	66
68	30
69	22
70	15
71	13
72	10
73	10
74	7
75	7
76	6
77	6
78	5
79	78
80	36
81	26
82	18
83	16
84	12
85	12
86	9
87	8
88	7
89	7