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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 2 |
| 4 | 13 |
| 5 | 27 |
| 6 | 140 |
| 7 | 392 |
| 8 | 1882 |
| 9 | 6289 |
| 10 | 28906 |
| 11 | 107949 |
| 12 | 486438 |
| 13 | 1948638 |
| 14 | 8730438 |
| 15 | 36611160 |
| 16 | 164259758 |
| 17 | 710530289 |
| 18 | 3203433595 |
| 19 | 14163150429 |
| 20 | 64260242637 |
| 21 | 288694503092 |
| 22 | 1318679597635 |
| 23 | 5996837692998 |
| 24 | 27572301084897 |
| 25 | 126595556379751 |
| 26 | 585652882733959 |
| 27 | 2709967750078764 |
| 28 | 12607711205847168 |
[1,0,2,2,13,27,140,392,1882,6289,28906,107949, 486438,1948638,8730438,36611160,164259758, 710530289,3203433595,14163150429,64260242637, 288694503092,1318679597635,5996837692998, 27572301084897,126595556379751,585652882733959, 2709967750078764,12607711205847168] |