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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 4 |
| 3 | 6 |
| 4 | 224 |
| 5 | 1330 |
| 6 | 42912 |
| 7 | 548114 |
| 8 | 18337440 |
| 9 | 382829346 |
| 10 | 14098368080 |
| 11 | 413342914402 |
| 12 | 17124811116624 |
| 13 | 644015140354898 |
| 14 | 30163665817167456 |
| 15 | 1375047846420311730 |
| 16 | 72583022771706823232 |
| 17 | 3866142693873431519554 |
| 18 | 228486372085027819754928 |
| 19 | 13871056133441358772777154 |
[1,0,4,6,224,1330,42912,548114,18337440,382829346, 14098368080,413342914402,17124811116624, 644015140354898,30163665817167456, 1375047846420311730,72583022771706823232, 3866142693873431519554,228486372085027819754928, 13871056133441358772777154] |