| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 23 |
| 4 | 151 |
| 5 | 1074 |
| 6 | 8059 |
| 7 | 62814 |
| 8 | 503619 |
| 9 | 4126954 |
| 10 | 34411602 |
| 11 | 291025337 |
| 12 | 2490377810 |
| 13 | 21523367553 |
| 14 | 187603609077 |
| 15 | 1647252368595 |
| 16 | 14556722879278 |
| 17 | 129366008725176 |
| 18 | 1155458240271571 |
| 19 | 10366549508487178 |
| 20 | 93382085749705066 |
| 21 | 844255894224907354 |
[1,1,4,23,151,1074,8059,62814,503619,4126954, 34411602,291025337,2490377810,21523367553, 187603609077,1647252368595,14556722879278, 129366008725176,1155458240271571, 10366549508487178,93382085749705066, 844255894224907354] |