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 | 6 |
| 3 | 9 |
| 4 | 56 |
| 5 | -300 |
| 6 | 3942 |
| 7 | -48412 |
| 8 | 639264 |
| 9 | -8785098 |
| 10 | 124733000 |
| 11 | -1817441901 |
| 12 | 27047510136 |
| 13 | -409669978497 |
| 14 | 6297861697848 |
| 15 | -98055605511675 |
| 16 | 1543575781461888 |
| 17 | -24533312413314948 |
| 18 | 393242952308487588 |
| 19 | -6350814254230701986 |