| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 20 |
| 4 | 117 |
| 5 | 503 |
| 6 | 1750 |
| 7 | 5209 |
| 8 | 13751 |
| 9 | 33000 |
| 10 | 73282 |
| 11 | 152581 |
| 12 | 300872 |
| 13 | 566293 |
| 14 | 1023724 |
| 15 | 1786462 |
| 16 | 3021818 |
| 17 | 4971616 |
| 18 | 7978746 |
| 19 | 12521114 |
| 20 | 19254543 |
| 21 | 29066411 |
| 22 | 43142066 |
| 23 | 63046335 |
| 24 | 90822745 |
| 25 | 129113400 |
| 26 | 181302810 |
| 27 | 251689347 |
| 28 | 345688410 |
| 29 | 470071817 |
[0,2,20,117,503,1750,5209,13751,33000,73282, 152581,300872,566293,1023724,1786462,3021818, 4971616,7978746,12521114,19254543,29066411, 43142066,63046335,90822745,129113400,181302810, 251689347,345688410,470071817] |