A002123 - cp's OEIS frontend

A002123 a(1) = 0, a(2) = 0; for n > 2, a(n) - a(n-3) - a(n-5) - ... - a(n-p) = n if n is prime, otherwise = 0, where p = largest prime < n.

n	a(n)
1	0
2	0
3	3
4	0
5	5
6	-3
7	7
8	-8
9	3
10	-15
11	22
12	-15
13	39
14	-35
15	38
16	-72
17	85
18	-111
19	152
20	-175
21	241
22	-308
23	414
24	-551
25	655
26	-897
27	1164
28	-1463
29	2001
30	-2538
31	3286
32	-4296
33	5503
34	-7259
35	9357
36	-12147
37	15910
38	-20406
39	26640
40	-34703
41	44854
42	-58481
43	75809
44	-98340

[0, 0, 3, 0, 5, -3, 7, -8, 3, -15, 22, -15, 39, -35, 38, -72, 85, -111, 152, -175, 241, -308, 414, -551, 655, -897, 1164, -1463, 2001, -2538, 3286, -4296, 5503, -7259, 9357, -12147, 15910, -20406, 26640, -34703, 44854, -58481, 75809, -98340]

cp's OEIS Frontend

A002123 a(1) = 0, a(2) = 0; for n > 2, a(n) - a(n-3) - a(n-5) - ... - a(n-p) = n if n is prime, otherwise = 0, where p = largest prime < n.

Table of values

List of values