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 | 0 |
| 2 | -2 |
| 3 | -6 |
| 4 | -16 |
| 5 | -55 |
| 6 | -288 |
| 7 | -2128 |
| 8 | -19808 |
| 9 | -219546 |
| 10 | -2816530 |
| 11 | -41002236 |
| 12 | -666782136 |
| 13 | -11961352104 |
| 14 | -234327748900 |
| 15 | -4972665181170 |
| 16 | -113552835539328 |
| 17 | -2774993356571920 |
| 18 | -72238332282154344 |
| 19 | -1995222148760626392 |
| 20 | -58268719729725843880 |
| 21 | -1793842001139571701696 |