The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 89 |
| 4 | 580 |
| 5 | 4009 |
| 6 | 28857 |
| 7 | 213967 |
| 8 | 1622869 |
| 9 | 12531090 |
| 10 | 98171544 |
| 11 | 778364379 |
| 12 | 6233789872 |
| 13 | 50355710215 |
| 14 | 409790010350 |
| 15 | 3356429972859 |
| 16 | 27647745771339 |
| 17 | 228890532343859 |
| 18 | 1903475080613014 |
| 19 | 15893483726218904 |
| 20 | 133190665385526309 |
| 21 | 1119863488613216952 |
[1,3,15,89,580,4009,28857,213967,1622869,12531090, 98171544,778364379,6233789872,50355710215, 409790010350,3356429972859,27647745771339, 228890532343859,1903475080613014, 15893483726218904,133190665385526309, 1119863488613216952] |