A004018 - cp's OEIS frontend

A004018 Theta series of square lattice (or number of ways of writing n as a sum of 2 squares). Often denoted by r(n) or r_2(n).

n	a(n)
0	1
1	4
2	4
3	0
4	4
5	8
6	0
7	0
8	4
9	4
10	8
11	0
12	0
13	8
14	0
15	0
16	4
17	8
18	4
19	0
20	8
21	0
22	0
23	0
24	0
25	12
26	8
27	0
28	0
29	8
30	0
31	0
32	4
33	0
34	8
35	0
36	4
37	8
38	0
39	0
40	8
41	8
42	0
43	0
44	0
45	8
46	0
47	0
48	0
49	4
50	12
51	0
52	8
53	8
54	0
55	0
56	0
57	0
58	8
59	0
60	0
61	8
62	0
63	0
64	4
65	16
66	0
67	0
68	8
69	0
70	0
71	0
72	4
73	8
74	8
75	0
76	0
77	0
78	0
79	0
80	8
81	4
82	8
83	0
84	0
85	16
86	0
87	0
88	0
89	8
90	8
91	0
92	0
93	0
94	0
95	0
96	0
97	8
98	4
99	0
100	12
101	8

[1, 4, 4, 0, 4, 8, 0, 0, 4, 4, 8, 0, 0, 8, 0, 0, 4, 8, 4, 0, 8, 0, 0, 0, 0, 12, 8, 0, 0, 8, 0, 0, 4, 0, 8, 0, 4, 8, 0, 0, 8, 8, 0, 0, 0, 8, 0, 0, 0, 4, 12, 0, 8, 8, 0, 0, 0, 0, 8, 0, 0, 8, 0, 0, 4, 16, 0, 0, 8, 0, 0, 0, 4, 8, 8, 0, 0, 0, 0, 0, 8, 4, 8, 0, 0, 16, 0, 0, 0, 8, 8, 0, 0, 0, 0, 0, 0, 8, 4, 0, 12, 8]

cp's OEIS Frontend

A004018 Theta series of square lattice (or number of ways of writing n as a sum of 2 squares). Often denoted by r(n) or r_2(n).

Table of values

List of values

n	a(n)
0	1
1	4
2	4
3	0
4	4
5	8
6	0
7	0
8	4
9	4
10	8
11	0
12	0
13	8
14	0
15	0
16	4
17	8
18	4
19	0
20	8
21	0
22	0
23	0
24	0
25	12
26	8
27	0
28	0
29	8
30	0
31	0
32	4
33	0
34	8
35	0
36	4
37	8
38	0
39	0
40	8
41	8
42	0
43	0
44	0
45	8
46	0
47	0
48	0
49	4
50	12
51	0
52	8
53	8
54	0
55	0
56	0
57	0
58	8
59	0
60	0
61	8
62	0
63	0
64	4
65	16
66	0
67	0
68	8
69	0
70	0
71	0
72	4
73	8
74	8
75	0
76	0
77	0
78	0
79	0
80	8
81	4
82	8
83	0
84	0
85	16
86	0
87	0
88	0
89	8
90	8
91	0
92	0
93	0
94	0
95	0
96	0
97	8
98	4
99	0
100	12
101	8

n	a(n)
0	1
1	4
2	4
3	0
4	4
5	8
6	0
7	0
8	4
9	4
10	8
11	0
12	0
13	8
14	0
15	0
16	4
17	8
18	4
19	0
20	8
21	0
22	0
23	0
24	0
25	12
26	8
27	0
28	0
29	8
30	0
31	0
32	4
33	0
34	8
35	0
36	4
37	8
38	0
39	0
40	8
41	8
42	0
43	0
44	0
45	8
46	0
47	0
48	0
49	4
50	12
51	0
52	8
53	8
54	0
55	0
56	0
57	0
58	8
59	0
60	0
61	8
62	0
63	0
64	4
65	16
66	0
67	0
68	8
69	0
70	0
71	0
72	4
73	8
74	8
75	0
76	0
77	0
78	0
79	0
80	8
81	4
82	8
83	0
84	0
85	16
86	0
87	0
88	0
89	8
90	8
91	0
92	0
93	0
94	0
95	0
96	0
97	8
98	4
99	0
100	12
101	8

n	a(n)
0	1
1	4
2	4
3	0
4	4
5	8
6	0
7	0
8	4
9	4
10	8
11	0
12	0
13	8
14	0
15	0
16	4
17	8
18	4
19	0
20	8
21	0
22	0
23	0
24	0
25	12
26	8
27	0
28	0
29	8
30	0
31	0
32	4
33	0
34	8
35	0
36	4
37	8
38	0
39	0
40	8
41	8
42	0
43	0
44	0
45	8
46	0
47	0
48	0
49	4
50	12
51	0
52	8
53	8
54	0
55	0
56	0
57	0
58	8
59	0
60	0
61	8
62	0
63	0
64	4
65	16
66	0
67	0
68	8
69	0
70	0
71	0
72	4
73	8
74	8
75	0
76	0
77	0
78	0
79	0
80	8
81	4
82	8
83	0
84	0
85	16
86	0
87	0
88	0
89	8
90	8
91	0
92	0
93	0
94	0
95	0
96	0
97	8
98	4
99	0
100	12
101	8