The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 9 |
| 3 | 30 |
| 4 | 90 |
| 5 | 248 |
| 6 | 650 |
| 7 | 1560 |
| 8 | 3560 |
| 9 | 7680 |
| 10 | 15786 |
| 11 | 31076 |
| 12 | 58905 |
| 13 | 107768 |
| 14 | 191180 |
| 15 | 329664 |
| 16 | 554038 |
| 17 | 909558 |
| 18 | 1461655 |
| 19 | 2302950 |
| 20 | 3563482 |
| 21 | 5422392 |
| 22 | 8124040 |
| 23 | 11997648 |
| 24 | 17482295 |
| 25 | 25156872 |
| 26 | 35779092 |
| 27 | 50330364 |
| 28 | 70072640 |
| 29 | 96615760 |
| 30 | 131999058 |
| 31 | 178786960 |
| 32 | 240186182 |
| 33 | 320179470 |
[1,2,9,30,90,248,650,1560,3560,7680,15786,31076, 58905,107768,191180,329664,554038,909558,1461655, 2302950,3563482,5422392,8124040,11997648,17482295, 25156872,35779092,50330364,70072640,96615760, 131999058,178786960,240186182,320179470] |