| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 72 |
| 3 | 264 |
| 4 | 2184 |
| 5 | 18897 |
| 6 | 213931 |
| 7 | 1964108 |
| 8 | 19450547 |
| 9 | 202140736 |
| 10 | 2027372089 |
| 11 | 20586190481 |
| 12 | 210496700285 |
| 13 | 2143793481874 |
| 14 | 21847592218744 |
| 15 | 223011991274682 |
| 16 | 2275397535129226 |
| 17 | 23213772911675819 |
| 18 | 236905932785631153 |
[0,72,264,2184,18897,213931,1964108,19450547, 202140736,2027372089,20586190481,210496700285, 2143793481874,21847592218744,223011991274682, 2275397535129226,23213772911675819, 236905932785631153] |