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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 42 |
| 5 | 608 |
| 6 | 10986 |
| 7 | 240492 |
| 8 | 6167112 |
| 9 | 181154848 |
| 10 | 5995624710 |
| 11 | 220711502648 |
| 12 | 8943846698096 |
| 13 | 395588177834784 |
| 14 | 18962600075658460 |
| 15 | 979198125493716492 |
| 16 | 54189002212286942316 |
| 17 | 3199366560075461850320 |
| 18 | 200730550064907653703510 |
| 19 | 13336507142191259122442532 |
| 20 | 935401326531455246646557760 |
| 21 | 69066745767857553528070539760 |
| 22 | 5355032622687046432711489319940 |
[1,0,1,4,42,608,10986,240492,6167112,181154848, 5995624710,220711502648,8943846698096, 395588177834784,18962600075658460, 979198125493716492,54189002212286942316, 3199366560075461850320,200730550064907653703510, 13336507142191259122442532, 935401326531455246646557760, 69066745767857553528070539760, 5355032622687046432711489319940] |