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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 2 |
| 3 | 9 |
| 4 | 41 |
| 5 | 189 |
| 6 | 880 |
| 7 | 4131 |
| 8 | 19522 |
| 9 | 92763 |
| 10 | 442798 |
| 11 | 2121795 |
| 12 | 10200477 |
| 13 | 49176639 |
| 14 | 237661176 |
| 15 | 1151032005 |
| 16 | 5585185425 |
| 17 | 27146751885 |
| 18 | 132145210270 |
| 19 | 644128990155 |
| 20 | 3143590707235 |
| 21 | 15358979381175 |
| 22 | 75117256339240 |
| 23 | 367723284610905 |
[0,0,2,9,41,189,880,4131,19522,92763,442798, 2121795,10200477,49176639,237661176,1151032005, 5585185425,27146751885,132145210270,644128990155, 3143590707235,15358979381175,75117256339240, 367723284610905] |