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 | 3 |
| 3 | -22 |
| 4 | 147 |
| 5 | -1009 |
| 6 | 6912 |
| 7 | -47377 |
| 8 | 324723 |
| 9 | -2225686 |
| 10 | 15255075 |
| 11 | -104559841 |
| 12 | 716663808 |
| 13 | -4912086817 |
| 14 | 33667943907 |
| 15 | -230763520534 |
| 16 | 1581676699827 |
| 17 | -10840973378257 |
| 18 | 74305136947968 |
| 19 | -509294985257521 |
| 20 | 3490759759854675 |