This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | -1 |
| 5 | 3 |
| 6 | -6 |
| 7 | 15 |
| 8 | -36 |
| 9 | 91 |
| 10 | -232 |
| 11 | 603 |
| 12 | -1585 |
| 13 | 4213 |
| 14 | -11298 |
| 15 | 30537 |
| 16 | -83097 |
| 17 | 227475 |
| 18 | -625992 |
| 19 | 1730787 |
| 20 | -4805595 |
| 21 | 13393689 |
| 22 | -37458330 |
| 23 | 105089229 |
| 24 | -295673994 |
| 25 | 834086421 |
| 26 | -2358641376 |
| 27 | 6684761125 |
| 28 | -18985057351 |
| 29 | 54022715451 |
| 30 | -154000562758 |
| 31 | 439742222071 |
| 32 | -1257643249140 |