The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 9 |
| 3 | 34 |
| 4 | 123 |
| 5 | 440 |
| 6 | 1573 |
| 7 | 5642 |
| 8 | 20332 |
| 9 | 73644 |
| 10 | 268090 |
| 11 | 980628 |
| 12 | 3603065 |
| 13 | 13293540 |
| 14 | 49234605 |
| 15 | 182991450 |
| 16 | 682341000 |
| 17 | 2551955340 |
| 18 | 9570762990 |
| 19 | 35985909180 |
| 20 | 135628219350 |
| 21 | 512302356384 |
| 22 | 1939078493154 |
| 23 | 7353556121924 |
| 24 | 27936898370248 |
| 25 | 106313496846200 |
[2,9,34,123,440,1573,5642,20332,73644,268090, 980628,3603065,13293540,49234605,182991450, 682341000,2551955340,9570762990,35985909180, 135628219350,512302356384,1939078493154, 7353556121924,27936898370248,106313496846200] |