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 | 3 |
| 2 | 9 |
| 3 | 21 |
| 4 | 9 |
| 5 | -297 |
| 6 | -2421 |
| 7 | -12933 |
| 8 | -52407 |
| 9 | -145293 |
| 10 | -35091 |
| 11 | 2954097 |
| 12 | 25228971 |
| 13 | 142080669 |
| 14 | 602217261 |
| 15 | 1724917221 |
| 16 | 283305033 |
| 17 | -38852066421 |
| 18 | -337425235479 |
| 19 | -1938308236731 |
| 20 | -8364863310291 |
| 21 | -24286959061533 |
| 22 | -3011589296289 |
| 23 | 574023003011199 |
| 24 | 5028616107443691 |