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| n | a(n) |
|---|---|
| 4 | 1 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 70 |
| 9 | 252 |
| 10 | 420 |
| 11 | 660 |
| 12 | 35640 |
| 13 | 271700 |
| 14 | 1389388 |
| 15 | 5137860 |
| 16 | 79463020 |
| 17 | 905649500 |
| 18 | 7336909980 |
| 19 | 48400150764 |
| 20 | 573924746400 |
| 21 | 7735300382250 |
| 22 | 85942063340210 |
| 23 | 795156908528290 |
| 24 | 9670781421636258 |
| 25 | 143772253669334950 |
| 26 | 1993964186469438950 |
| 27 | 24015169625528033550 |
[1,0,0,0,70,252,420,660,35640,271700,1389388, 5137860,79463020,905649500,7336909980,48400150764, 573924746400,7735300382250,85942063340210, 795156908528290,9670781421636258, 143772253669334950,1993964186469438950, 24015169625528033550] |