The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 10 |
| 6 | 30 |
| 7 | 88 |
| 8 | 252 |
| 9 | 712 |
| 10 | 1992 |
| 11 | 5537 |
| 12 | 15323 |
| 13 | 42286 |
| 14 | 116506 |
| 15 | 320773 |
| 16 | 883191 |
| 17 | 2433112 |
| 18 | 6709832 |
| 19 | 18529067 |
| 20 | 51251265 |
| 21 | 142021430 |
| 22 | 394336930 |
| 23 | 1097215414 |
| 24 | 3059549286 |
| 25 | 8550284176 |
| 26 | 23947824960 |
| 27 | 67221675367 |
| 28 | 189102714045 |
| 29 | 533104654538 |
[0,0,1,3,10,30,88,252,712,1992,5537,15323,42286, 116506,320773,883191,2433112,6709832,18529067, 51251265,142021430,394336930,1097215414, 3059549286,8550284176,23947824960,67221675367, 189102714045,533104654538] |