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) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 30 |
| 5 | -330 |
| 6 | 257070 |
| 7 | 128005692870 |
| 8 | 23279147893155496537470 |
| 9 | 388475314992168993748220639081347493631827670 |