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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 3 |
| 3 | 6 |
| 4 | 19 |
| 5 | 48 |
| 6 | 141 |
| 7 | 378 |
| 8 | 1063 |
| 9 | 2920 |
| 10 | 8115 |
| 11 | 22418 |
| 12 | 62123 |
| 13 | 171876 |
| 14 | 475919 |
| 15 | 1317250 |
| 16 | 3646681 |
| 17 | 10094356 |
| 18 | 27943739 |
| 19 | 77353070 |
| 20 | 214129845 |
| 21 | 592752572 |
| 22 | 1640859689 |
| 23 | 4542223926 |
| 24 | 12573787053 |
| 25 | 34806745800 |
| 26 | 96352029241 |
| 27 | 266721635838 |
| 28 | 738338745535 |
| 29 | 2043868995512 |
[1,0,3,6,19,48,141,378,1063,2920,8115,22418,62123, 171876,475919,1317250,3646681,10094356,27943739, 77353070,214129845,592752572,1640859689, 4542223926,12573787053,34806745800,96352029241, 266721635838,738338745535,2043868995512] |