The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 70 |
| 5 | 1228 |
| 6 | 28884 |
| 7 | 853792 |
| 8 | 30426112 |
| 9 | 1270005984 |
| 10 | 60788427616 |
| 11 | 3282799648960 |
| 12 | 197474811497664 |
| 13 | 13095421797740416 |
| 14 | 949181590215488128 |
| 15 | 74658555720475765248 |
| 16 | 6333634998698003763712 |
| 17 | 576475075653068190813184 |
| 18 | 56036347601660951779132416 |
| 19 | 5793905340158437271916457984 |
[1,1,6,70,1228,28884,853792,30426112,1270005984, 60788427616,3282799648960,197474811497664, 13095421797740416,949181590215488128, 74658555720475765248,6333634998698003763712, 576475075653068190813184, 56036347601660951779132416, 5793905340158437271916457984] |