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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 11 |
| 4 | 35 |
| 5 | 111 |
| 6 | 365 |
| 7 | 1221 |
| 8 | 4160 |
| 9 | 14371 |
| 10 | 50251 |
| 11 | 177503 |
| 12 | 632514 |
| 13 | 2271027 |
| 14 | 8208259 |
| 15 | 29840993 |
| 16 | 109049568 |
| 17 | 400352639 |
| 18 | 1475929092 |
| 19 | 5461571729 |
| 20 | 20279092033 |
| 21 | 75531360153 |
| 22 | 282123848574 |
| 23 | 1056539226257 |
| 24 | 3966214054639 |
| 25 | 14922195004703 |
| 26 | 56258116929483 |
| 27 | 212505815364639 |
| 28 | 804142811583006 |
[1,1,4,11,35,111,365,1221,4160,14371,50251,177503, 632514,2271027,8208259,29840993,109049568, 400352639,1475929092,5461571729,20279092033, 75531360153,282123848574,1056539226257, 3966214054639,14922195004703,56258116929483, 212505815364639,804142811583006] |