A047161 - cp's OEIS frontend

A047161 Number of nonempty subsets of {1,2,...,n} in which exactly 1/3 of the elements are <= n/2.

n	a(n)
1	0
2	0
3	1
4	2
5	6
6	9
7	21
8	30
9	70
10	100
11	235
12	335
13	791
14	1127
15	2681
16	3822
17	9150
18	13050
19	31401
20	44802
21	108262
22	154517
23	374715
24	534963
25	1301235
26	1858155
27	4531423
28	6472167
29	15818791
30	22597759
31	55339849
32	79067374
33	193962894
34	277164294
35	680963509
36	973184312
37	2394289028
38	3422117189

[0, 0, 1, 2, 6, 9, 21, 30, 70, 100, 235, 335, 791, 1127, 2681, 3822, 9150, 13050, 31401, 44802, 108262, 154517, 374715, 534963, 1301235, 1858155, 4531423, 6472167, 15818791, 22597759, 55339849, 79067374, 193962894, 277164294, 680963509, 973184312, 2394289028, 3422117189]

cp's OEIS Frontend

A047161 Number of nonempty subsets of {1,2,...,n} in which exactly 1/3 of the elements are <= n/2.

Table of values

List of values