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 | 0 |
| 3 | 1 |
| 4 | -2 |
| 5 | 6 |
| 6 | -17 |
| 7 | 49 |
| 8 | -141 |
| 9 | 406 |
| 10 | -1169 |
| 11 | 3366 |
| 12 | -9692 |
| 13 | 27907 |
| 14 | -80355 |
| 15 | 231373 |
| 16 | -666212 |
| 17 | 1918281 |
| 18 | -5523470 |
| 19 | 15904198 |
| 20 | -45794313 |
| 21 | 131859469 |
| 22 | -379674209 |
| 23 | 1093228314 |
| 24 | -3147825473 |
| 25 | 9063802210 |
| 26 | -26098178316 |
| 27 | 75146709475 |
| 28 | -216376326215 |
| 29 | 623030800329 |
| 30 | -1793945691512 |
| 31 | 5165460748321 |