| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 17 |
| 5 | 40 |
| 6 | 125 |
| 7 | 354 |
| 8 | 1159 |
| 9 | 3774 |
| 10 | 13113 |
| 11 | 46426 |
| 12 | 171027 |
| 13 | 644038 |
| 14 | 2493848 |
| 15 | 9867688 |
| 16 | 39922991 |
| 17 | 164747459 |
| 18 | 693093407 |
| 19 | 2968918400 |
| 20 | 12940917244 |
| 21 | 57353242370 |
| 22 | 258306634422 |
| 23 | 1181572250326 |
| 24 | 5486982683756 |
| 25 | 25856584485254 |
[1,1,3,6,17,40,125,354,1159,3774,13113,46426, 171027,644038,2493848,9867688,39922991,164747459, 693093407,2968918400,12940917244,57353242370, 258306634422,1181572250326,5486982683756, 25856584485254] |