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 | 1 |
| 2 | 2 |
| 3 | -3 |
| 4 | -48 |
| 5 | -339 |
| 6 | -1008 |
| 7 | 10737 |
| 8 | 237312 |
| 9 | 2362041 |
| 10 | 5432832 |
| 11 | -318158523 |
| 12 | -7615254528 |
| 13 | -87216236379 |
| 14 | 173049219072 |
| 15 | 33959321252217 |
| 16 | 851545449234432 |
| 17 | 9561733579228401 |
| 18 | -129701862228492288 |
| 19 | -9445723672920941043 |
| 20 | -239815723596207095808 |
| 21 | -2109465061216228379619 |