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 | -5 |
| 2 | 13 |
| 3 | 15 |
| 4 | -1321 |
| 5 | -335 |
| 6 | 10219 |
| 7 | 16955 |
| 8 | -3573841 |
| 9 | -1503963 |
| 10 | 879397865 |
| 11 | 204957775 |
| 12 | -851608366093 |
| 13 | -39666688711 |
| 14 | 2959809512491 |
| 15 | 10337889346275 |
| 16 | -74944106556227777 |
| 17 | -3489994294713779 |
| 18 | 6362557475056495393 |
| 19 | 1481439997178305655 |
| 20 | -8686827386554851319211 |