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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 7 |
| 5 | 68 |
| 6 | 837 |
| 7 | 11863 |
| 8 | 189503 |
| 9 | 3377341 |
| 10 | 66564396 |
| 11 | 1439304777 |
| 12 | 33902511983 |
| 13 | 864514417843 |
| 14 | 23735220814661 |
| 15 | 698226455579492 |
| 16 | 21914096529153695 |
| 17 | 731009183350476805 |
| 18 | 25829581529376423945 |
| 19 | 963786767538027630275 |
| 20 | 37871891147795243899204 |
| 21 | 1563295398737378236910447 |
[1,0,0,1,7,68,837,11863,189503,3377341,66564396, 1439304777,33902511983,864514417843, 23735220814661,698226455579492,21914096529153695, 731009183350476805,25829581529376423945, 963786767538027630275,37871891147795243899204, 1563295398737378236910447] |