The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 10 |
| 5 | 23 |
| 6 | 63 |
| 7 | 154 |
| 8 | 446 |
| 9 | 1135 |
| 10 | 3416 |
| 11 | 8947 |
| 12 | 27712 |
| 13 | 74204 |
| 14 | 235041 |
| 15 | 640552 |
| 16 | 2065849 |
| 17 | 5711840 |
| 18 | 18696838 |
| 19 | 52321747 |
| 20 | 173413647 |
| 21 | 490279035 |
| 22 | 1642287831 |
| 23 | 4684178185 |
| 24 | 15834649146 |
| 25 | 45511151647 |
| 26 | 155077912223 |
| 27 | 448722569787 |
| 28 | 1539743907074 |
| 29 | 4481866870316 |
| 30 | 15474663284941 |
[1,1,2,4,10,23,63,154,446,1135,3416,8947,27712, 74204,235041,640552,2065849,5711840,18696838, 52321747,173413647,490279035,1642287831, 4684178185,15834649146,45511151647,155077912223, 448722569787,1539743907074,4481866870316, 15474663284941] |