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 | -4 |
| 2 | 6 |
| 3 | -24 |
| 4 | 41 |
| 5 | -145 |
| 6 | 273 |
| 7 | -886 |
| 8 | 1789 |
| 9 | -5457 |
| 10 | 11605 |
| 11 | -33807 |
| 12 | 74761 |
| 13 | -210366 |
| 14 | 479256 |
| 15 | -1313465 |
| 16 | 3061242 |
| 17 | -8222492 |
| 18 | 19501429 |
| 19 | -51579259 |
| 20 | 123983182 |
| 21 | -324067194 |
| 22 | 787044384 |
| 23 | -2038584810 |
| 24 | 4990387355 |
| 25 | -12836179872 |
| 26 | 31614557443 |
| 27 | -80883958143 |
| 28 | 200146505560 |
| 29 | -509959672813 |