The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | 2 |
| 4 | -10 |
| 5 | 30 |
| 6 | -84 |
| 7 | 244 |
| 8 | -722 |
| 9 | 2126 |
| 10 | -6252 |
| 11 | 18364 |
| 12 | -53988 |
| 13 | 158668 |
| 14 | -466408 |
| 15 | 1370792 |
| 16 | -4029154 |
| 17 | 11842222 |
| 18 | -34806972 |
| 19 | 102303468 |
| 20 | -300690348 |
| 21 | 883782404 |
| 22 | -2597604952 |
| 23 | 7634834648 |
| 24 | -22440207764 |
| 25 | 65955900268 |
| 26 | -193856647736 |
| 27 | 569780485080 |
| 28 | -1674690451976 |
[1,1,0,2,-10,30,-84,244,-722,2126,-6252,18364, -53988,158668,-466408,1370792,-4029154,11842222, -34806972,102303468,-300690348,883782404, -2597604952,7634834648,-22440207764,65955900268, -193856647736,569780485080,-1674690451976] |