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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 21 |
| 3 | 56 |
| 4 | 126 |
| 5 | 252 |
| 6 | 463 |
| 7 | 804 |
| 8 | 1365 |
| 9 | 2366 |
| 10 | 4368 |
| 11 | 8736 |
| 12 | 18565 |
| 13 | 40410 |
| 14 | 87381 |
| 15 | 184604 |
| 16 | 379050 |
| 17 | 758100 |
| 18 | 1486675 |
| 19 | 2884776 |
| 20 | 5592405 |
| 21 | 10919090 |
| 22 | 21572460 |
| 23 | 43144920 |
| 24 | 87087001 |
| 25 | 176565486 |
| 26 | 357913941 |
| 27 | 723002336 |
| 28 | 1453179126 |
| 29 | 2906358252 |
[1,6,21,56,126,252,463,804,1365,2366,4368,8736, 18565,40410,87381,184604,379050,758100,1486675, 2884776,5592405,10919090,21572460,43144920, 87087001,176565486,357913941,723002336,1453179126, 2906358252] |