The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 21 |
| 6 | 52 |
| 7 | 134 |
| 8 | 355 |
| 9 | 957 |
| 10 | 2608 |
| 11 | 7154 |
| 12 | 19701 |
| 13 | 54379 |
| 14 | 150302 |
| 15 | 415762 |
| 16 | 1150609 |
| 17 | 3185147 |
| 18 | 8818620 |
| 19 | 24418128 |
| 20 | 67615743 |
| 21 | 187239359 |
| 22 | 518506932 |
| 23 | 1435875288 |
| 24 | 3976322869 |
| 25 | 11011542937 |
| 26 | 30494088494 |
| 27 | 84446895364 |
| 28 | 233857897749 |
| 29 | 647620493541 |
[0,1,2,4,9,21,52,134,355,957,2608,7154,19701, 54379,150302,415762,1150609,3185147,8818620, 24418128,67615743,187239359,518506932,1435875288, 3976322869,11011542937,30494088494,84446895364, 233857897749,647620493541] |