The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 8 |
| 2 | 64 |
| 3 | 280 |
| 4 | 1156 |
| 5 | 4720 |
| 6 | 18960 |
| 7 | 74869 |
| 8 | 293495 |
| 9 | 1143065 |
| 10 | 4435997 |
| 11 | 17166670 |
| 12 | 66321486 |
| 13 | 255904884 |
| 14 | 986647975 |
| 15 | 3801894402 |
| 16 | 14644645685 |
| 17 | 56395631397 |
| 18 | 217139104510 |
| 19 | 835947689845 |
| 20 | 3217998048544 |
| 21 | 12387073741629 |
| 22 | 47679941911196 |
[8,64,280,1156,4720,18960,74869,293495,1143065, 4435997,17166670,66321486,255904884,986647975, 3801894402,14644645685,56395631397,217139104510, 835947689845,3217998048544,12387073741629, 47679941911196] |