| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 50 |
| 3 | 357 |
| 4 | 2549 |
| 5 | 18200 |
| 6 | 129949 |
| 7 | 927843 |
| 8 | 6624850 |
| 9 | 47301793 |
| 10 | 337737401 |
| 11 | 2411463600 |
| 12 | 17217982601 |
| 13 | 122937341807 |
| 14 | 877779375250 |
| 15 | 6267392968557 |
| 16 | 44749530155149 |
| 17 | 319514104054600 |
| 18 | 2281348258537349 |
| 19 | 16288951913816043 |
| 20 | 116304011655249650 |
| 21 | 830417033500563593 |
[1,7,50,357,2549,18200,129949,927843,6624850, 47301793,337737401,2411463600,17217982601, 122937341807,877779375250,6267392968557, 44749530155149,319514104054600,2281348258537349, 16288951913816043,116304011655249650, 830417033500563593] |