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 | 4 |
| 2 | -7 |
| 3 | -118 |
| 4 | -399 |
| 5 | 0 |
| 6 | 7849 |
| 7 | 61318 |
| 8 | 357857 |
| 9 | 1894076 |
| 10 | 9665625 |
| 11 | 48667074 |
| 12 | 243891793 |
| 13 | 1220331832 |
| 14 | 6102977801 |
| 15 | 30516818750 |
| 16 | 152586842049 |
| 17 | 762938033268 |
| 18 | 3814695376057 |
| 19 | 19073483852026 |
| 20 | 95367428440625 |