| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 14 |
| 4 | 108 |
| 5 | 930 |
| 6 | 8700 |
| 7 | 86598 |
| 8 | 904176 |
| 9 | 9804516 |
| 10 | 109624536 |
| 11 | 1257136130 |
| 12 | 14726063264 |
| 13 | 175650153588 |
| 14 | 2128038439176 |
| 15 | 26133761328150 |
| 16 | 324786698542440 |
| 17 | 4079191750094776 |
| 18 | 51716838331485472 |
| 19 | 661227615895716180 |
| 20 | 8518677674587163584 |
[0,1,2,14,108,930,8700,86598,904176,9804516, 109624536,1257136130,14726063264,175650153588, 2128038439176,26133761328150,324786698542440, 4079191750094776,51716838331485472, 661227615895716180,8518677674587163584] |