The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 21 |
| 2 | 89 |
| 3 | 378 |
| 4 | 1610 |
| 5 | 6877 |
| 6 | 29461 |
| 7 | 126591 |
| 8 | 545627 |
| 9 | 2359152 |
| 10 | 10233188 |
| 11 | 44533546 |
| 12 | 194450722 |
| 13 | 851923695 |
| 14 | 3745257911 |
| 15 | 16522347429 |
| 16 | 73145533817 |
| 17 | 324971178262 |
| 18 | 1448957138290 |
| 19 | 6483809640888 |
| 20 | 29119030669064 |
| 21 | 131250471466965 |
[21,89,378,1610,6877,29461,126591,545627,2359152, 10233188,44533546,194450722,851923695,3745257911, 16522347429,73145533817,324971178262, 1448957138290,6483809640888,29119030669064, 131250471466965] |