The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 40 |
| 4 | 239 |
| 5 | 1648 |
| 6 | 12778 |
| 7 | 109476 |
| 8 | 1023520 |
| 9 | 10341878 |
| 10 | 112067820 |
| 11 | 1294254184 |
| 12 | 15847382977 |
| 13 | 204827368606 |
| 14 | 2784056034014 |
| 15 | 39665514607872 |
| 16 | 590684848605779 |
| 17 | 9170941154737032 |
| 18 | 148120725648168260 |
| 19 | 2483657480026985432 |
| 20 | 43157660169344697996 |
| 21 | 775898068395820783674 |
[1,2,8,40,239,1648,12778,109476,1023520,10341878, 112067820,1294254184,15847382977,204827368606, 2784056034014,39665514607872,590684848605779, 9170941154737032,148120725648168260, 2483657480026985432,43157660169344697996, 775898068395820783674] |