A238405 - cp's OEIS frontend

A238405 a(n) = |{0 < k < n: prime(k) + pi(n-k) is a triangular number}|, where pi(.) is given by A000720.

n	a(n)
1	0
2	0
3	2
4	0
5	1
6	0
7	1
8	2
9	3
10	3
11	2
12	2
13	1
14	3
15	3
16	1
17	2
18	1
19	2
20	5
21	3
22	3
23	4
24	1
25	2
26	2
27	3
28	3
29	1
30	2
31	3
32	4
33	5
34	6
35	5
36	3
37	2
38	2
39	3
40	3
41	2
42	5
43	5
44	4
45	3
46	2
47	4
48	3
49	2
50	3
51	3
52	2
53	4
54	6
55	4
56	6
57	9
58	8
59	6
60	4
61	3
62	2
63	3
64	4
65	5
66	3
67	5
68	6
69	5
70	5
71	1
72	1
73	3
74	5
75	4
76	4
77	9
78	7
79	6
80	6
81	4
82	6
83	3
84	3
85	5
86	8
87	8
88	5
89	4
90	7
91	8
92	4
93	5
94	3
95	2
96	3
97	4
98	4
99	4
100	4

[0, 0, 2, 0, 1, 0, 1, 2, 3, 3, 2, 2, 1, 3, 3, 1, 2, 1, 2, 5, 3, 3, 4, 1, 2, 2, 3, 3, 1, 2, 3, 4, 5, 6, 5, 3, 2, 2, 3, 3, 2, 5, 5, 4, 3, 2, 4, 3, 2, 3, 3, 2, 4, 6, 4, 6, 9, 8, 6, 4, 3, 2, 3, 4, 5, 3, 5, 6, 5, 5, 1, 1, 3, 5, 4, 4, 9, 7, 6, 6, 4, 6, 3, 3, 5, 8, 8, 5, 4, 7, 8, 4, 5, 3, 2, 3, 4, 4, 4, 4]

cp's OEIS Frontend

A238405 a(n) = |{0 < k < n: prime(k) + pi(n-k) is a triangular number}|, where pi(.) is given by A000720.

Table of values

List of values

n	a(n)
1	0
2	0
3	2
4	0
5	1
6	0
7	1
8	2
9	3
10	3
11	2
12	2
13	1
14	3
15	3
16	1
17	2
18	1
19	2
20	5
21	3
22	3
23	4
24	1
25	2
26	2
27	3
28	3
29	1
30	2
31	3
32	4
33	5
34	6
35	5
36	3
37	2
38	2
39	3
40	3
41	2
42	5
43	5
44	4
45	3
46	2
47	4
48	3
49	2
50	3
51	3
52	2
53	4
54	6
55	4
56	6
57	9
58	8
59	6
60	4
61	3
62	2
63	3
64	4
65	5
66	3
67	5
68	6
69	5
70	5
71	1
72	1
73	3
74	5
75	4
76	4
77	9
78	7
79	6
80	6
81	4
82	6
83	3
84	3
85	5
86	8
87	8
88	5
89	4
90	7
91	8
92	4
93	5
94	3
95	2
96	3
97	4
98	4
99	4
100	4

n	a(n)
1	0
2	0
3	2
4	0
5	1
6	0
7	1
8	2
9	3
10	3
11	2
12	2
13	1
14	3
15	3
16	1
17	2
18	1
19	2
20	5
21	3
22	3
23	4
24	1
25	2
26	2
27	3
28	3
29	1
30	2
31	3
32	4
33	5
34	6
35	5
36	3
37	2
38	2
39	3
40	3
41	2
42	5
43	5
44	4
45	3
46	2
47	4
48	3
49	2
50	3
51	3
52	2
53	4
54	6
55	4
56	6
57	9
58	8
59	6
60	4
61	3
62	2
63	3
64	4
65	5
66	3
67	5
68	6
69	5
70	5
71	1
72	1
73	3
74	5
75	4
76	4
77	9
78	7
79	6
80	6
81	4
82	6
83	3
84	3
85	5
86	8
87	8
88	5
89	4
90	7
91	8
92	4
93	5
94	3
95	2
96	3
97	4
98	4
99	4
100	4

n	a(n)
1	0
2	0
3	2
4	0
5	1
6	0
7	1
8	2
9	3
10	3
11	2
12	2
13	1
14	3
15	3
16	1
17	2
18	1
19	2
20	5
21	3
22	3
23	4
24	1
25	2
26	2
27	3
28	3
29	1
30	2
31	3
32	4
33	5
34	6
35	5
36	3
37	2
38	2
39	3
40	3
41	2
42	5
43	5
44	4
45	3
46	2
47	4
48	3
49	2
50	3
51	3
52	2
53	4
54	6
55	4
56	6
57	9
58	8
59	6
60	4
61	3
62	2
63	3
64	4
65	5
66	3
67	5
68	6
69	5
70	5
71	1
72	1
73	3
74	5
75	4
76	4
77	9
78	7
79	6
80	6
81	4
82	6
83	3
84	3
85	5
86	8
87	8
88	5
89	4
90	7
91	8
92	4
93	5
94	3
95	2
96	3
97	4
98	4
99	4
100	4