The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 42 |
| 4 | 924 |
| 5 | 36300 |
| 6 | 2265960 |
| 7 | 206703840 |
| 8 | 25945444560 |
| 9 | 4287205253520 |
| 10 | 901822916010240 |
| 11 | 235245784759302240 |
| 12 | 74515547291697610560 |
| 13 | 28171404151229273014080 |
| 14 | 12529985068482904127064960 |
| 15 | 6476871523103017023955968000 |
| 16 | 3850268179365489288889549267200 |
[1,1,4,42,924,36300,2265960,206703840,25945444560, 4287205253520,901822916010240,235245784759302240, 74515547291697610560,28171404151229273014080, 12529985068482904127064960, 6476871523103017023955968000, 3850268179365489288889549267200] |