The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 22 |
| 3 | 1638 |
| 4 | 47454 |
| 5 | 904530 |
| 6 | 13529862 |
| 7 | 172576362 |
| 8 | 1966038698 |
| 9 | 20583987894 |
| 10 | 201838423616 |
| 11 | 1878183167916 |
| 12 | 16744919877108 |
| 13 | 144061342087884 |
| 14 | 1202594886126228 |
| 15 | 9783039293041644 |
| 16 | 77823360967288812 |
| 17 | 607079393002409364 |
| 18 | 4654603707195506610 |
| 19 | 35144449267872359562 |
| 20 | 261740341786424075106 |
[0,0,22,1638,47454,904530,13529862,172576362, 1966038698,20583987894,201838423616,1878183167916, 16744919877108,144061342087884,1202594886126228, 9783039293041644,77823360967288812, 607079393002409364,4654603707195506610, 35144449267872359562,261740341786424075106] |