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 | 1 |
| 4 | -5 |
| 5 | -74 |
| 6 | -679 |
| 7 | -4899 |
| 8 | -17289 |
| 9 | 325837 |
| 10 | 10627109 |
| 11 | 199348590 |
| 12 | 2684041427 |
| 13 | 15872610469 |
| 14 | -546948563407 |
| 15 | -27499774835519 |
| 16 | -778467357484561 |
| 17 | -15311413773551790 |
| 18 | -125363405319188419 |
| 19 | 6452292137017871097 |
| 20 | 436442148982835915339 |
| 21 | 16494863323310244977581 |