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 | 1 |
| 3 | -2 |
| 4 | -11 |
| 5 | 16 |
| 6 | 301 |
| 7 | -104 |
| 8 | -15287 |
| 9 | -20096 |
| 10 | 1239481 |
| 11 | 4427776 |
| 12 | -146243459 |
| 13 | -954111872 |
| 14 | 23567903269 |
| 15 | 243390205696 |
| 16 | -4951201340399 |
| 17 | -75389245067264 |
| 18 | 1307274054385393 |
| 19 | 28248828019830784 |
| 20 | -420773143716828539 |