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 | 0 |
| 2 | 3 |
| 3 | -9 |
| 4 | -27 |
| 5 | 459 |
| 6 | 243 |
| 7 | -58563 |
| 8 | 338985 |
| 9 | 11581623 |
| 10 | -206336889 |
| 11 | -2610099207 |
| 12 | 128764066797 |
| 13 | 37135699587 |
| 14 | -90848500643781 |
| 15 | 1216300295221749 |
| 16 | 68623945856512209 |
| 17 | -2410073970973057809 |
| 18 | -44786917868989757553 |
| 19 | 4171855691698864732305 |
| 20 | -8174731579262161250859 |