The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 4 |
| 4 | 4 |
| 5 | 31 |
| 6 | 86 |
| 7 | 449 |
| 8 | 1968 |
| 9 | 10420 |
| 10 | 56582 |
| 11 | 333235 |
| 12 | 2069772 |
| 13 | 13606113 |
| 14 | 94065232 |
| 15 | 682242552 |
| 16 | 5175100432 |
| 17 | 40954340995 |
| 18 | 337362555010 |
| 19 | 2886922399649 |
| 20 | 25616738519384 |
| 21 | 235313456176512 |
| 22 | 2234350827008170 |
| 23 | 21899832049913999 |
| 24 | 221292603495494488 |
| 25 | 2302631998398438321 |
[1,0,4,4,31,86,449,1968,10420,56582,333235, 2069772,13606113,94065232,682242552,5175100432, 40954340995,337362555010,2886922399649, 25616738519384,235313456176512,2234350827008170, 21899832049913999,221292603495494488, 2302631998398438321] |