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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 4 |
| 5 | 8 |
| 6 | 28 |
| 7 | 108 |
| 8 | 372 |
| 9 | 1280 |
| 10 | 4776 |
| 11 | 18464 |
| 12 | 71840 |
| 13 | 282856 |
| 14 | 1134696 |
| 15 | 4623328 |
| 16 | 19044552 |
| 17 | 79217024 |
| 18 | 332678424 |
| 19 | 1409411128 |
| 20 | 6017276432 |
| 21 | 25869106896 |
| 22 | 111931476168 |
| 23 | 487189405200 |
| 24 | 2132112963608 |
| 25 | 9377901602688 |
| 26 | 41440635484904 |
| 27 | 183921242382848 |
| 28 | 819585479873264 |
| 29 | 3666044711577832 |
[1,0,0,2,4,8,28,108,372,1280,4776,18464,71840, 282856,1134696,4623328,19044552,79217024, 332678424,1409411128,6017276432,25869106896, 111931476168,487189405200,2132112963608, 9377901602688,41440635484904,183921242382848, 819585479873264,3666044711577832] |