| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 7 |
| 3 | 20 |
| 4 | 54 |
| 5 | 143 |
| 6 | 376 |
| 7 | 986 |
| 8 | 2583 |
| 9 | 6764 |
| 10 | 17710 |
| 11 | 46367 |
| 12 | 121392 |
| 13 | 317810 |
| 14 | 832039 |
| 15 | 2178308 |
| 16 | 5702886 |
| 17 | 14930351 |
| 18 | 39088168 |
| 19 | 102334154 |
| 20 | 267914295 |
| 21 | 701408732 |
| 22 | 1836311902 |
| 23 | 4807526975 |
| 24 | 12586269024 |
| 25 | 32951280098 |
| 26 | 86267571271 |
| 27 | 225851433716 |
[0,2,7,20,54,143,376,986,2583,6764,17710,46367, 121392,317810,832039,2178308,5702886,14930351, 39088168,102334154,267914295,701408732,1836311902, 4807526975,12586269024,32951280098,86267571271, 225851433716] |