The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 8 |
| 2 | 28 |
| 3 | 109 |
| 4 | 472 |
| 5 | 2639 |
| 6 | 13134 |
| 7 | 64593 |
| 8 | 329236 |
| 9 | 1675126 |
| 10 | 8446443 |
| 11 | 42786562 |
| 12 | 217265141 |
| 13 | 1100720836 |
| 14 | 5579444003 |
| 15 | 28303389818 |
| 16 | 143512396002 |
| 17 | 727722225397 |
| 18 | 3690768784000 |
| 19 | 18716882745820 |
| 20 | 94919221030890 |
| 21 | 481381697348861 |
[8,28,109,472,2639,13134,64593,329236,1675126, 8446443,42786562,217265141,1100720836,5579444003, 28303389818,143512396002,727722225397, 3690768784000,18716882745820,94919221030890, 481381697348861] |