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 | 0 |
| 1 | 1 |
| 2 | -3 |
| 3 | 10 |
| 4 | -40 |
| 5 | 213 |
| 6 | -1383 |
| 7 | 11002 |
| 8 | -100616 |
| 9 | 1062625 |
| 10 | -12508067 |
| 11 | 164543938 |
| 12 | -2368224032 |
| 13 | 37311284645 |
| 14 | -634900302775 |
| 15 | 11658800863330 |
| 16 | -229004281334768 |
| 17 | 4804124787023265 |
| 18 | -106986109080667043 |
| 19 | 2524701174424967130 |
| 20 | -62860054802079553016 |
| 21 | 1648303843512405478485 |