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 | 2 |
| 2 | -6 |
| 3 | 34 |
| 4 | -238 |
| 5 | 1858 |
| 6 | -15510 |
| 7 | 135490 |
| 8 | -1223134 |
| 9 | 11320066 |
| 10 | -106830502 |
| 11 | 1024144482 |
| 12 | -9945711566 |
| 13 | 97634828354 |
| 14 | -967298498358 |
| 15 | 9659274283650 |
| 16 | -97119829841854 |
| 17 | 982391779220482 |
| 18 | -9990160542904134 |
| 19 | 102074758837531810 |
| 20 | -1047391288012377774 |
| 21 | 10788532748880319298 |