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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 0 |
| 4 | -1 |
| 5 | 4 |
| 6 | -12 |
| 7 | -3 |
| 8 | 640 |
| 9 | -9721 |
| 10 | 107849 |
| 11 | -766116 |
| 12 | -5716810 |
| 13 | 438016259 |
| 14 | -13557651987 |
| 15 | 318299775147 |
| 16 | -5284369281919 |
| 17 | -5483686862123 |
| 18 | 6119663470743306 |
| 19 | -388801742002632589 |
| 20 | 17841761552418336070 |
| 21 | -645131407697518621805 |
| 22 | 14383670984970068901209 |
| 23 | 384858376828629625293001 |