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 | 768 |
| 5 | 19460 |
| 6 | 637200 |
| 7 | 25724916 |
| 8 | 1233957312 |
| 9 | 68591031120 |
| 10 | 4338982958400 |
| 11 | 307907317681920 |
| 12 | 24229505587541760 |
| 13 | 2094548798610726432 |
| 14 | 197370092438311892736 |
| 15 | 20140182770328963216000 |
| 16 | 2213078753956025271214080 |
| 17 | 260601290312643875434817280 |
[1,1,4,42,768,19460,637200,25724916,1233957312, 68591031120,4338982958400,307907317681920, 24229505587541760,2094548798610726432, 197370092438311892736,20140182770328963216000, 2213078753956025271214080, 260601290312643875434817280] |