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| n | a(n) |
|---|---|
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 0 |
| 7 | 0 |
| 8 | 8 |
| 9 | 24 |
| 10 | 90 |
| 11 | 240 |
| 12 | 492 |
| 13 | 1064 |
| 14 | 2452 |
| 15 | 5814 |
| 16 | 14766 |
| 17 | 38400 |
| 18 | 98846 |
| 19 | 252902 |
| 20 | 644456 |
| 21 | 1641944 |
| 22 | 4201380 |
| 23 | 10802792 |
| 24 | 27907392 |
| 25 | 72395562 |
| 26 | 188325960 |
| 27 | 491013312 |
| 28 | 1283101256 |
| 29 | 3359669780 |
| 30 | 8813687070 |
| 31 | 23166783438 |
[1,1,1,0,0,8,24,90,240,492,1064,2452,5814,14766, 38400,98846,252902,644456,1641944,4201380, 10802792,27907392,72395562,188325960,491013312, 1283101256,3359669780,8813687070,23166783438] |