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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | 1 |
| 5 | 8 |
| 6 | 26 |
| 7 | 194 |
| 8 | 1142 |
| 9 | 9736 |
| 10 | 81384 |
| 11 | 823392 |
| 12 | 8738016 |
| 13 | 104336880 |
| 14 | 1328270880 |
| 15 | 18419317968 |
| 16 | 272291315376 |
| 17 | 4312675967232 |
| 18 | 72478365279360 |
| 19 | 1292173575000192 |
| 20 | 24314102888206464 |
| 21 | 482046102448383744 |
| 22 | 10037081891973037824 |
[0,1,0,1,1,8,26,194,1142,9736,81384,823392, 8738016,104336880,1328270880,18419317968, 272291315376,4312675967232,72478365279360, 1292173575000192,24314102888206464, 482046102448383744,10037081891973037824] |