The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 12 |
| 3 | 48 |
| 4 | 201 |
| 5 | 885 |
| 6 | 4116 |
| 7 | 20298 |
| 8 | 106365 |
| 9 | 592455 |
| 10 | 3503532 |
| 11 | 21946620 |
| 12 | 145210305 |
| 13 | 1011726417 |
| 14 | 7400390052 |
| 15 | 56668826118 |
| 16 | 453116188821 |
| 17 | 3774297532467 |
| 18 | 32682069679548 |
| 19 | 293632972911048 |
| 20 | 2732593851548985 |
| 21 | 26299137526992525 |
| 22 | 261387306941467188 |
| 23 | 2679392140776188706 |
[1,3,12,48,201,885,4116,20298,106365,592455, 3503532,21946620,145210305,1011726417,7400390052, 56668826118,453116188821,3774297532467, 32682069679548,293632972911048,2732593851548985, 26299137526992525,261387306941467188, 2679392140776188706] |