The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 52 |
| 5 | 170 |
| 6 | 792 |
| 7 | 2958 |
| 8 | 14057 |
| 9 | 54619 |
| 10 | 264029 |
| 11 | 1068087 |
| 12 | 5208579 |
| 13 | 21555125 |
| 14 | 105790375 |
| 15 | 446084237 |
| 16 | 2198685109 |
| 17 | 9399635429 |
| 18 | 46473502878 |
| 19 | 200903485754 |
| 20 | 995565199085 |
| 21 | 4342682420690 |
| 22 | 21556860426720 |
| 23 | 94738071265023 |
| 24 | 470894637973974 |
| 25 | 2082599114595994 |
| 26 | 10362169084078158 |
| 27 | 46076752691587189 |
[1,1,4,12,52,170,792,2958,14057,54619,264029, 1068087,5208579,21555125,105790375,446084237, 2198685109,9399635429,46473502878,200903485754, 995565199085,4342682420690,21556860426720, 94738071265023,470894637973974,2082599114595994, 10362169084078158,46076752691587189] |