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 | -1 |
| 2 | 1 |
| 3 | -3 |
| 4 | 6 |
| 5 | -17 |
| 6 | 43 |
| 7 | -125 |
| 8 | 348 |
| 9 | -1029 |
| 10 | 3020 |
| 11 | -9116 |
| 12 | 27567 |
| 13 | -84620 |
| 14 | 260949 |
| 15 | -812053 |
| 16 | 2539208 |
| 17 | -7989121 |
| 18 | 25244540 |
| 19 | -80136851 |
| 20 | 255325972 |
| 21 | -816447638 |
| 22 | 2618870068 |
| 23 | -8425244209 |
| 24 | 27176810469 |
| 25 | -87879769383 |
| 26 | 284813417885 |
| 27 | -925013053556 |
| 28 | 3010106492409 |
| 29 | -9813119711706 |