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 | 12 |
| 3 | -40 |
| 4 | 124 |
| 5 | -408 |
| 6 | 1272 |
| 7 | -4176 |
| 8 | 13020 |
| 9 | -42808 |
| 10 | 133096 |
| 11 | -439344 |
| 12 | 1358872 |
| 13 | -4514800 |
| 14 | 13853040 |
| 15 | -46469280 |
| 16 | 140945820 |
| 17 | -479312760 |
| 18 | 1430085000 |
| 19 | -4958382960 |
| 20 | 14453014920 |
| 21 | -51500944080 |
| 22 | 145230007440 |
| 23 | -537922074720 |
| 24 | 1446902948184 |
| 25 | -5662012752048 |
| 26 | 14228883685392 |