The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 25 |
| 5 | 126 |
| 6 | 756 |
| 7 | 5298 |
| 8 | 42387 |
| 9 | 381485 |
| 10 | 3814852 |
| 11 | 41963378 |
| 12 | 503560537 |
| 13 | 6546286983 |
| 14 | 91648017770 |
| 15 | 1374720266550 |
| 16 | 21995524264802 |
| 17 | 373923912501650 |
| 18 | 6730630425029702 |
| 19 | 127881978075564346 |
| 20 | 2557639561511286935 |
[1,2,6,25,126,756,5298,42387,381485,3814852, 41963378,503560537,6546286983,91648017770, 1374720266550,21995524264802,373923912501650, 6730630425029702,127881978075564346, 2557639561511286935] |