| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 44 |
| 4 | 332 |
| 5 | 2476 |
| 6 | 18136 |
| 7 | 130824 |
| 8 | 933372 |
| 9 | 6610676 |
| 10 | 46603616 |
| 11 | 327603904 |
| 12 | 2298933412 |
| 13 | 16115938476 |
| 14 | 112906938696 |
| 15 | 790735321784 |
| 16 | 5536710117452 |
| 17 | 38763269947876 |
| 18 | 271368229299376 |
| 19 | 1899679393564464 |
| 20 | 13298164198917492 |
[0,1,6,44,332,2476,18136,130824,933372,6610676, 46603616,327603904,2298933412,16115938476, 112906938696,790735321784,5536710117452, 38763269947876,271368229299376,1899679393564464, 13298164198917492] |