The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 5 |
| 5 | 15 |
| 6 | 49 |
| 7 | 168 |
| 8 | 594 |
| 9 | 2150 |
| 10 | 7931 |
| 11 | 29718 |
| 12 | 112814 |
| 13 | 432957 |
| 14 | 1677050 |
| 15 | 6547856 |
| 16 | 25742454 |
| 17 | 101819101 |
| 18 | 404885649 |
| 19 | 1617725220 |
| 20 | 6491296371 |
| 21 | 26147447557 |
| 22 | 105691741392 |
| 23 | 428578725720 |
| 24 | 1742927971200 |
| 25 | 7106956875720 |
| 26 | 29050379285808 |
| 27 | 119015289279194 |
| 28 | 488612294241992 |
| 29 | 2009889728675210 |
[1,1,2,5,15,49,168,594,2150,7931,29718,112814, 432957,1677050,6547856,25742454,101819101, 404885649,1617725220,6491296371,26147447557, 105691741392,428578725720,1742927971200, 7106956875720,29050379285808,119015289279194, 488612294241992,2009889728675210] |