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 | -6 |
| 2 | 21 |
| 3 | -56 |
| 4 | 126 |
| 5 | -252 |
| 6 | 463 |
| 7 | -804 |
| 8 | 1365 |
| 9 | -2366 |
| 10 | 4368 |
| 11 | -8736 |
| 12 | 18565 |
| 13 | -40410 |
| 14 | 87381 |
| 15 | -184604 |
| 16 | 379050 |
| 17 | -758100 |
| 18 | 1486675 |
| 19 | -2884776 |
| 20 | 5592405 |
| 21 | -10919090 |
| 22 | 21572460 |
| 23 | -43144920 |
| 24 | 87087001 |
| 25 | -176565486 |
| 26 | 357913941 |
| 27 | -723002336 |