The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 21 |
| 2 | 157 |
| 3 | 1230 |
| 4 | 10485 |
| 5 | 85500 |
| 6 | 706534 |
| 7 | 5834429 |
| 8 | 48122349 |
| 9 | 397252886 |
| 10 | 3278636644 |
| 11 | 27062747191 |
| 12 | 223377950567 |
| 13 | 1843848878602 |
| 14 | 15220263846832 |
| 15 | 125635656973478 |
| 16 | 1037081229322655 |
| 17 | 8560832928119444 |
| 18 | 70667136506972822 |
| 19 | 583340972841489677 |
[21,157,1230,10485,85500,706534,5834429,48122349, 397252886,3278636644,27062747191,223377950567, 1843848878602,15220263846832,125635656973478, 1037081229322655,8560832928119444, 70667136506972822,583340972841489677] |