| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 44 |
| 3 | 278 |
| 4 | 1756 |
| 5 | 11092 |
| 6 | 70064 |
| 7 | 442568 |
| 8 | 2795536 |
| 9 | 17658352 |
| 10 | 111541184 |
| 11 | 704563808 |
| 12 | 4450465216 |
| 13 | 28111918912 |
| 14 | 177572443904 |
| 15 | 1121658501248 |
| 16 | 7085095895296 |
| 17 | 44753892374272 |
| 18 | 282693546036224 |
| 19 | 1785669060965888 |
| 20 | 11279401457867776 |
| 21 | 71247746869138432 |
[1,7,44,278,1756,11092,70064,442568,2795536, 17658352,111541184,704563808,4450465216, 28111918912,177572443904,1121658501248, 7085095895296,44753892374272,282693546036224, 1785669060965888,11279401457867776, 71247746869138432] |