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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | -2 |
| 4 | 1 |
| 5 | 9 |
| 6 | -16 |
| 7 | -73 |
| 8 | -145 |
| 9 | 1442 |
| 10 | 3951 |
| 11 | -49121 |
| 12 | 273184 |
| 13 | 4095073 |
| 14 | -13134671 |
| 15 | -609740514 |
| 16 | -7877081935 |
| 17 | 206841213449 |
| 18 | 153991537616 |
| 19 | -138343392420553 |
| 20 | 3626684171795871 |
| 21 | 187758843981508546 |
| 22 | 2146096698964614559 |