| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 131776 |
| 5 | 3470549 |
| 6 | 37807680 |
| 7 | 371453327 |
| 8 | 2166664192 |
| 9 | 10453333842 |
| 10 | 47955097344 |
| 11 | 177644368014 |
| 12 | 539461479744 |
| 13 | 1776632877223 |
| 14 | 4936852235840 |
| 15 | 12181833395949 |
| 16 | 30549903200768 |
| 17 | 72297760469620 |
| 18 | 155915494771968 |
[0,0,0,131776,3470549,37807680,371453327, 2166664192,10453333842,47955097344,177644368014, 539461479744,1776632877223,4936852235840, 12181833395949,30549903200768,72297760469620, 155915494771968] |