The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 15 |
| 3 | 107 |
| 4 | 751 |
| 5 | 5258 |
| 6 | 36808 |
| 7 | 257658 |
| 8 | 1803607 |
| 9 | 12625251 |
| 10 | 88376759 |
| 11 | 618637314 |
| 12 | 4330461200 |
| 13 | 30313228402 |
| 14 | 212192598815 |
| 15 | 1485348191707 |
| 16 | 10397437341951 |
| 17 | 72782061393658 |
| 18 | 509474429755608 |
| 19 | 3566321008289258 |
[2,15,107,751,5258,36808,257658,1803607,12625251, 88376759,618637314,4330461200,30313228402, 212192598815,1485348191707,10397437341951, 72782061393658,509474429755608,3566321008289258] |