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 | 0 |
| 1 | 1 |
| 2 | -1 |
| 3 | 3 |
| 4 | -4 |
| 5 | 5 |
| 6 | -1 |
| 7 | 7 |
| 8 | -64 |
| 9 | 9 |
| 10 | 1319 |
| 11 | 11 |
| 12 | -49204 |
| 13 | 13 |
| 14 | 2653559 |
| 15 | 15 |
| 16 | -196707424 |
| 17 | 17 |
| 18 | 19194804719 |
| 19 | 19 |
| 20 | -2385684870724 |
| 21 | 21 |
| 22 | 367985503366799 |
| 23 | 23 |
| 24 | -68980888889771104 |
| 25 | 25 |
| 26 | 15445553274667315799 |
| 27 | 27 |
| 28 | -4071626956018456576564 |
| 29 | 29 |