The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 5 |
| 5 | 13 |
| 6 | 55 |
| 7 | 193 |
| 8 | 941 |
| 9 | 4081 |
| 10 | 22351 |
| 11 | 113761 |
| 12 | 694565 |
| 13 | 4030153 |
| 14 | 27107095 |
| 15 | 175738753 |
| 16 | 1289775821 |
| 17 | 9209233921 |
| 18 | 73147903471 |
| 19 | 568928274961 |
| 20 | 4857161139365 |
| 21 | 40796613003433 |
| 22 | 372190216061335 |
| 23 | 3352314486348433 |
| 24 | 32518958606637101 |
| 25 | 312271731474218881 |
[0,0,1,1,5,13,55,193,941,4081,22351,113761,694565, 4030153,27107095,175738753,1289775821,9209233921, 73147903471,568928274961,4857161139365, 40796613003433,372190216061335,3352314486348433, 32518958606637101,312271731474218881] |