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 | -30 |
| 3 | -237 |
| 4 | -1000 |
| 5 | -3005 |
| 6 | -7056 |
| 7 | -11767 |
| 8 | 7552 |
| 9 | 303831 |
| 10 | 3528800 |
| 11 | 39755749 |
| 12 | 478752768 |
| 13 | 6226649507 |
| 14 | 87177753376 |
| 15 | 1307673608625 |
| 16 | 20922788839424 |
| 17 | 355687426676143 |
| 18 | 6402373703838432 |
| 19 | 121645100406355901 |
| 20 | 2432902008173440000 |