| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 8 |
| 3 | 26 |
| 4 | 90 |
| 5 | 322 |
| 6 | 1176 |
| 7 | 4356 |
| 8 | 16302 |
| 9 | 61490 |
| 10 | 233376 |
| 11 | 890188 |
| 12 | 3409588 |
| 13 | 13104756 |
| 14 | 50517200 |
| 15 | 195234120 |
| 16 | 756197910 |
| 17 | 2934686610 |
| 18 | 11408741520 |
| 19 | 44420399100 |
| 20 | 173191792620 |
| 21 | 676104403260 |
| 22 | 2642356838160 |
| 23 | 10337529691320 |
| 24 | 40481034410700 |
[1,3,8,26,90,322,1176,4356,16302,61490,233376, 890188,3409588,13104756,50517200,195234120, 756197910,2934686610,11408741520,44420399100, 173191792620,676104403260,2642356838160, 10337529691320,40481034410700] |