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 | -4 |
| 3 | 9 |
| 4 | -25 |
| 5 | 82 |
| 6 | -284 |
| 7 | 969 |
| 8 | -3185 |
| 9 | 10082 |
| 10 | -30964 |
| 11 | 93129 |
| 12 | -276745 |
| 13 | 818482 |
| 14 | -2421644 |
| 15 | 7188489 |
| 16 | -21428705 |
| 17 | 64121282 |
| 18 | -192388324 |
| 19 | 578087049 |
| 20 | -1737827065 |
| 21 | 5223134482 |
| 22 | -15690187004 |
| 23 | 47105428809 |
| 24 | -141351839825 |
| 25 | 424023394082 |
| 26 | -1271763913684 |