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 | -4 |
| 3 | -5 |
| 4 | 57 |
| 5 | 548 |
| 6 | 1967 |
| 7 | -13561 |
| 8 | -302718 |
| 9 | -2589819 |
| 10 | -2709911 |
| 11 | 300801642 |
| 12 | 5531279773 |
| 13 | 48708116819 |
| 14 | -142678610012 |
| 15 | -13947271486097 |
| 16 | -277586590571059 |
| 17 | -2741155101562764 |
| 18 | 15789174378252979 |
| 19 | 1332483468802350235 |
| 20 | 31222229349684528898 |
| 21 | 380895661222461566625 |