n | a(n) |
---|---|
1 | 0 |
2 | 6 |
3 | 18 |
4 | 136 |
5 | 654 |
6 | 3972 |
7 | 21778 |
8 | 127226 |
9 | 727214 |
10 | 4237154 |
11 | 24617576 |
12 | 144049162 |
13 | 843945398 |
14 | 4961892900 |
15 | 29226194746 |
16 | 172530718840 |
17 | 1020187713214 |
18 | 6042341555988 |
19 | 35837121558046 |
20 | 212824919490178 |
21 | 1265353059527832 |
[0,6,18,136,654,3972,21778,127226,727214,4237154, 24617576,144049162,843945398,4961892900, 29226194746,172530718840,1020187713214, 6042341555988,35837121558046,212824919490178, 1265353059527832] |