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 | -49 |
| 3 | -149 |
| 4 | 7201 |
| 5 | 37001 |
| 6 | -1763249 |
| 7 | -12863549 |
| 8 | 604273601 |
| 9 | 5749693201 |
| 10 | -266173427249 |
| 11 | -3141020027749 |
| 12 | 143254364959201 |
| 13 | 2027866381608601 |
| 14 | -91087470841872049 |
| 15 | -1510593937967892749 |
| 16 | 66805009193436144001 |
| 17 | 1275280159567750343201 |
| 18 | -55508977654852972057649 |