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 | 7 |
| 4 | 13 |
| 5 | 81 |
| 6 | 391 |
| 7 | 1093 |
| 8 | 18537 |
| 9 | 577 |
| 10 | 1013131 |
| 11 | -54339 |
| 12 | 39429853 |
| 13 | 424162753 |
| 14 | -4130181873 |
| 15 | 137131757701 |
| 16 | -1733851435439 |
| 17 | 29708533549953 |
| 18 | -337960798083053 |
| 19 | 3890007865959661 |
| 20 | -11844138798049659 |
| 21 | -662440203084569279 |
| 22 | 30135319297423429783 |