A216621 - cp's OEIS frontend

A216621 Triangle read by rows, n >= 1, 1 <= k <= n, T(n,k) = Sum_{c|n,d|k} phi(gcd(c,d)).

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

[1, 2, 4, 2, 4, 5, 3, 6, 6, 10, 2, 4, 4, 6, 7, 4, 8, 10, 12, 8, 20, 2, 4, 4, 6, 4, 8, 9, 4, 8, 8, 14, 8, 16, 8, 22, 3, 6, 8, 9, 6, 16, 6, 12, 17, 4, 8, 8, 12, 14, 16, 8, 16, 12, 28, 2, 4, 4, 6, 4, 8, 4, 8, 6, 8, 13, 6, 12, 15, 20, 12, 30, 12, 28, 24, 24, 12]

cp's OEIS Frontend

A216621 Triangle read by rows, n >= 1, 1 <= k <= n, T(n,k) = Sum_{c|n,d|k} phi(gcd(c,d)).

Table of values

List of values

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

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

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