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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 9 |
| 5 | 26 |
| 6 | 103 |
| 7 | 446 |
| 8 | 1964 |
| 9 | 8624 |
| 10 | 38467 |
| 11 | 172996 |
| 12 | 781826 |
| 13 | 3543506 |
| 14 | 16101962 |
| 15 | 73319508 |
| 16 | 334431875 |
| 17 | 1527675428 |
| 18 | 6987461432 |
| 19 | 31997430636 |
| 20 | 146680198680 |
| 21 | 673052434686 |
| 22 | 3091103533619 |
| 23 | 14208094465250 |
| 24 | 65356612821710 |
[0,0,2,9,26,103,446,1964,8624,38467,172996,781826, 3543506,16101962,73319508,334431875,1527675428, 6987461432,31997430636,146680198680,673052434686, 3091103533619,14208094465250,65356612821710] |