| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 36 |
| 3 | 294 |
| 4 | 2436 |
| 5 | 19814 |
| 6 | 162776 |
| 7 | 1333934 |
| 8 | 10937316 |
| 9 | 89651534 |
| 10 | 734979136 |
| 11 | 6025149574 |
| 12 | 49393306556 |
| 13 | 404916355574 |
| 14 | 3319433387656 |
| 15 | 27212098788254 |
| 16 | 223079838087956 |
| 17 | 1828767624421854 |
| 18 | 14991902921730896 |
| 19 | 122900877847563254 |
[4,36,294,2436,19814,162776,1333934,10937316, 89651534,734979136,6025149574,49393306556, 404916355574,3319433387656,27212098788254, 223079838087956,1828767624421854, 14991902921730896,122900877847563254] |