| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 28 |
| 3 | 88 |
| 4 | 400 |
| 5 | 1936 |
| 6 | 8368 |
| 7 | 38272 |
| 8 | 176320 |
| 9 | 800512 |
| 10 | 3661312 |
| 11 | 16761088 |
| 12 | 76588288 |
| 13 | 350288896 |
| 14 | 1602288640 |
| 15 | 7327467520 |
| 16 | 33513336832 |
| 17 | 153280811008 |
| 18 | 701043896320 |
| 19 | 3206335627264 |
| 20 | 14664712241152 |
| 21 | 67071268225024 |
| 22 | 306761100427264 |
[4,28,88,400,1936,8368,38272,176320,800512, 3661312,16761088,76588288,350288896,1602288640, 7327467520,33513336832,153280811008,701043896320, 3206335627264,14664712241152,67071268225024, 306761100427264] |