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 | 5 |
| 3 | 13 |
| 4 | -63 |
| 5 | -2279 |
| 6 | -51167 |
| 7 | -423387 |
| 8 | 13717889 |
| 9 | 885044593 |
| 10 | 37051519041 |
| 11 | 779965433149 |
| 12 | -14179999608959 |
| 13 | -2798466635425239 |
| 14 | -224720509492366495 |
| 15 | -11148988922254048619 |
| 16 | -300176114650473574143 |
| 17 | 18804123010954180467937 |
| 18 | 4351564646569010083711105 |