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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 15 |
| 5 | 41 |
| 6 | 108 |
| 7 | 281 |
| 8 | 735 |
| 9 | 1926 |
| 10 | 5043 |
| 11 | 13201 |
| 12 | 34560 |
| 13 | 90481 |
| 14 | 236883 |
| 15 | 620166 |
| 16 | 1623615 |
| 17 | 4250681 |
| 18 | 11128428 |
| 19 | 29134601 |
| 20 | 76275375 |
| 21 | 199691526 |
| 22 | 522799203 |
| 23 | 1368706081 |
| 24 | 3583319040 |
| 25 | 9381251041 |
| 26 | 24560434083 |
| 27 | 64300051206 |
| 28 | 168339719535 |
| 29 | 440719107401 |
| 30 | 1153817602668 |
[0,1,3,6,15,41,108,281,735,1926,5043,13201,34560, 90481,236883,620166,1623615,4250681,11128428, 29134601,76275375,199691526,522799203,1368706081, 3583319040,9381251041,24560434083,64300051206, 168339719535,440719107401,1153817602668] |