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 | 5 |
| 3 | -13 |
| 4 | 36 |
| 5 | -101 |
| 6 | 293 |
| 7 | -848 |
| 8 | 2523 |
| 9 | -7365 |
| 10 | 22402 |
| 11 | -64395 |
| 12 | 205285 |
| 13 | -541802 |
| 14 | 2057617 |
| 15 | -3403993 |
| 16 | 28685420 |
| 17 | 43885023 |
| 18 | 824532745 |
| 19 | 4878097904 |
| 20 | 44263112047 |
| 21 | 357891860463 |
| 22 | 3169228222338 |
| 23 | 28506399763969 |
| 24 | 266822555964441 |
| 25 | 2573194635922990 |
| 26 | 25606751525353741 |