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 | -16 |
| 4 | -82 |
| 5 | -476 |
| 6 | -2968 |
| 7 | -19360 |
| 8 | -130220 |
| 9 | -895592 |
| 10 | -6264656 |
| 11 | -44411968 |
| 12 | -318300080 |
| 13 | -2302042400 |
| 14 | -16777460032 |
| 15 | -123084642048 |
| 16 | -908175062994 |
| 17 | -6734680013532 |
| 18 | -50164119638328 |
| 19 | -375134475461088 |
| 20 | -2815268948389212 |
| 21 | -21195313970398536 |