The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 24 |
| 3 | 114 |
| 4 | 578 |
| 5 | 2859 |
| 6 | 14187 |
| 7 | 70982 |
| 8 | 353880 |
| 9 | 1763742 |
| 10 | 8792075 |
| 11 | 43834726 |
| 12 | 218552639 |
| 13 | 1089593715 |
| 14 | 5432145667 |
| 15 | 27082226021 |
| 16 | 135020029240 |
| 17 | 673148618666 |
| 18 | 3356010198589 |
| 19 | 16731535456995 |
| 20 | 83415827627182 |
| 21 | 415873350543689 |
[4,24,114,578,2859,14187,70982,353880,1763742, 8792075,43834726,218552639,1089593715,5432145667, 27082226021,135020029240,673148618666, 3356010198589,16731535456995,83415827627182, 415873350543689] |