The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 5 |
| 5 | 11 |
| 6 | 23 |
| 7 | 119 |
| 8 | 237 |
| 9 | 776 |
| 10 | 6665 |
| 11 | 16518 |
| 12 | 207953 |
| 13 | 892680 |
| 14 | 1824445 |
| 15 | 8374988 |
| 16 | 96208461 |
| 17 | 978217302 |
| 18 | 2059770725 |
| 19 | 18616884428 |
| 20 | 78013141907 |
| 21 | 158103168924 |
| 22 | 1386674113487 |
| 23 | 6734724875544 |
| 24 | 82189835767618 |
| 25 | 2013603833805429 |
| 26 | 9101106147506177 |
| 27 | 19147196940580651 |
[0,0,2,5,11,23,119,237,776,6665,16518,207953, 892680,1824445,8374988,96208461,978217302, 2059770725,18616884428,78013141907,158103168924, 1386674113487,6734724875544,82189835767618, 2013603833805429,9101106147506177, 19147196940580651] |