The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 18 |
| 4 | 63 |
| 5 | 162 |
| 6 | 540 |
| 7 | 1458 |
| 8 | 4536 |
| 9 | 13203 |
| 10 | 39852 |
| 11 | 118098 |
| 12 | 356238 |
| 13 | 1062882 |
| 14 | 3193020 |
| 15 | 9567396 |
| 16 | 28711665 |
| 17 | 86093442 |
| 18 | 258324066 |
| 19 | 774840978 |
| 20 | 2324645406 |
| 21 | 6973581924 |
| 22 | 20921060700 |
| 23 | 62762119218 |
| 24 | 188287473024 |
| 25 | 564859079523 |
| 26 | 1694580407532 |
[1,6,18,63,162,540,1458,4536,13203,39852,118098, 356238,1062882,3193020,9567396,28711665,86093442, 258324066,774840978,2324645406,6973581924, 20921060700,62762119218,188287473024,564859079523, 1694580407532] |