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 | 0 |
| 5 | -2 |
| 6 | 0 |
| 7 | 5 |
| 8 | 0 |
| 9 | -14 |
| 10 | 0 |
| 11 | 42 |
| 12 | 0 |
| 13 | -132 |
| 14 | 0 |
| 15 | 429 |
| 16 | 0 |
| 17 | -1430 |
| 18 | 0 |
| 19 | 4862 |
| 20 | 0 |
| 21 | -16796 |
| 22 | 0 |
| 23 | 58786 |
| 24 | 0 |
| 25 | -208012 |
| 26 | 0 |
| 27 | 742900 |
| 28 | 0 |
| 29 | -2674440 |
| 30 | 0 |
| 31 | 9694845 |
| 32 | 0 |
| 33 | -35357670 |
| 34 | 0 |
| 35 | 129644790 |
| 36 | 0 |
| 37 | -477638700 |
| 38 | 0 |
| 39 | 1767263190 |
| 40 | 0 |