n | a(n) |
---|---|
1 | 4 |
2 | 0 |
3 | 2 |
4 | 7 |
5 | 24 |
6 | 84 |
7 | 300 |
8 | 1089 |
9 | 4004 |
10 | 14872 |
11 | 55692 |
12 | 209950 |
13 | 795872 |
14 | 3031032 |
15 | 11589240 |
16 | 44462565 |
17 | 171085500 |
18 | 660009840 |
19 | 2551955340 |
20 | 9887121090 |
21 | 38374857840 |
22 | 149184555000 |
23 | 580807904040 |
24 | 2264193450090 |
25 | 8837215647624 |
26 | 34529741789904 |
27 | 135054066707000 |
[4,0,2,7,24,84,300,1089,4004,14872,55692,209950, 795872,3031032,11589240,44462565,171085500, 660009840,2551955340,9887121090,38374857840, 149184555000,580807904040,2264193450090, 8837215647624,34529741789904,135054066707000] |