| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 26 |
| 4 | 122 |
| 5 | 602 |
| 6 | 3062 |
| 7 | 15906 |
| 8 | 83906 |
| 9 | 447842 |
| 10 | 2412566 |
| 11 | 13094490 |
| 12 | 71513210 |
| 13 | 392592410 |
| 14 | 2164815590 |
| 15 | 11982792386 |
| 16 | 66548673282 |
| 17 | 370672213826 |
| 18 | 2069974290726 |
| 19 | 11586244722202 |
| 20 | 64986102400122 |
| 21 | 365183031749722 |
| 22 | 2055594717395926 |
| 23 | 11588727763937506 |
| 24 | 65425688924696002 |
[1,2,6,26,122,602,3062,15906,83906,447842,2412566, 13094490,71513210,392592410,2164815590, 11982792386,66548673282,370672213826, 2069974290726,11586244722202,64986102400122, 365183031749722,2055594717395926, 11588727763937506,65425688924696002] |