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 | 11 |
| 4 | -7 |
| 5 | 389 |
| 6 | -1031 |
| 7 | 19039 |
| 8 | -24431 |
| 9 | 1023497 |
| 10 | -4044079 |
| 11 | 225738611 |
| 12 | -1711460279 |
| 13 | 29974303501 |
| 14 | 4656373513 |
| 15 | 3798866053319 |
| 16 | -34131041040991 |
| 17 | 2131052083901969 |
| 18 | -23678368533941471 |
| 19 | 832900320313739227 |
| 20 | -4752766287768240359 |
| 21 | 148482851420849206421 |