| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 5 |
| 5 | 17 |
| 6 | 140 |
| 7 | 375 |
| 8 | 1090 |
| 9 | 11753 |
| 10 | 373581 |
| 11 | 1278347 |
| 12 | 13637279 |
| 13 | 163618153 |
| 14 | 27924949575 |
| 15 | 57188675627613 |
| 16 | 610029725544935 |
| 17 | 117122198574078151 |
| 18 | 19988890974450988558 |
| 19 | 239866235837773427391 |
| 20 | 12281151167363439030630 |
[0,1,3,5,17,140,375,1090,11753,373581,1278347, 13637279,163618153,27924949575,57188675627613, 610029725544935,117122198574078151, 19988890974450988558,239866235837773427391, 12281151167363439030630] |