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 | 2 |
| 3 | -4 |
| 4 | 8 |
| 5 | -15 |
| 6 | 23 |
| 7 | -14 |
| 8 | -95 |
| 9 | 616 |
| 10 | -2597 |
| 11 | 9280 |
| 12 | -29971 |
| 13 | 89283 |
| 14 | -245617 |
| 15 | 614122 |
| 16 | -1330205 |
| 17 | 2121789 |
| 18 | -134318 |
| 19 | -18870272 |
| 20 | 111955244 |
| 21 | -481559262 |
| 22 | 1783749762 |
| 23 | -5976975892 |
| 24 | 18406561660 |
| 25 | -52025500982 |
| 26 | 132347403714 |
| 27 | -285820317372 |
| 28 | 421120353772 |
| 29 | 271625450178 |
| 30 | -5772145145591 |