The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 12 |
| 3 | 89 |
| 4 | 574 |
| 5 | 3469 |
| 6 | 20065 |
| 7 | 114537 |
| 8 | 650819 |
| 9 | 3705824 |
| 10 | 21181267 |
| 11 | 121617211 |
| 12 | 701255335 |
| 13 | 4058735341 |
| 14 | 23565789117 |
| 15 | 137190976378 |
| 16 | 800437914689 |
| 17 | 4678794395883 |
| 18 | 27391873966579 |
| 19 | 160581355210547 |
| 20 | 942493889605853 |
[2,12,89,574,3469,20065,114537,650819,3705824, 21181267,121617211,701255335,4058735341, 23565789117,137190976378,800437914689, 4678794395883,27391873966579,160581355210547, 942493889605853] |