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 | -1 |
| 3 | -8 |
| 4 | 15 |
| 5 | 126 |
| 6 | -280 |
| 7 | -2400 |
| 8 | 5775 |
| 9 | 50050 |
| 10 | -126126 |
| 11 | -1100736 |
| 12 | 2858856 |
| 13 | 25069968 |
| 14 | -66512160 |
| 15 | -585307008 |
| 16 | 1577585295 |
| 17 | 13919870250 |
| 18 | -37978905250 |
| 19 | -335813478000 |
| 20 | 925166131890 |
| 21 | 8194328596740 |
| 22 | -22754499243840 |
| 23 | -201822515032320 |
| 24 | 564121960420200 |
| 25 | 5009403008531376 |