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 | -8 |
| 4 | 45 |
| 5 | 126 |
| 6 | -840 |
| 7 | -2400 |
| 8 | 17325 |
| 9 | 50050 |
| 10 | -378378 |
| 11 | -1100736 |
| 12 | 8576568 |
| 13 | 25069968 |
| 14 | -199536480 |
| 15 | -585307008 |
| 16 | 4732755885 |
| 17 | 13919870250 |
| 18 | -113936715750 |
| 19 | -335813478000 |
| 20 | 2775498395670 |
| 21 | 8194328596740 |
| 22 | -68263497731520 |
| 23 | -201822515032320 |