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 | -2 |
| 3 | -4 |
| 4 | -2 |
| 5 | 76 |
| 6 | 953 |
| 7 | 9103 |
| 8 | 77054 |
| 9 | 550457 |
| 10 | 2123247 |
| 11 | -32551171 |
| 12 | -1197444063 |
| 13 | -26019611323 |
| 14 | -478608682879 |
| 15 | -7915791047153 |
| 16 | -115777452314939 |
| 17 | -1320533985179144 |
| 18 | -3550854626237496 |
| 19 | 455708391448493954 |
| 20 | 21276221692251262984 |
| 21 | 703173682906460544467 |