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 | -7 |
| 3 | 49 |
| 4 | -399 |
| 5 | 3633 |
| 6 | -35511 |
| 7 | 363937 |
| 8 | -3858079 |
| 9 | 41951521 |
| 10 | -465296487 |
| 11 | 5243459409 |
| 12 | -59865074223 |
| 13 | 690979478481 |
| 14 | -8049598938135 |
| 15 | 94522387901505 |
| 16 | -1117615459764031 |
| 17 | 13294669980012865 |
| 18 | -158995530738069703 |
| 19 | 1910555096402418545 |
| 20 | -23056131790988675279 |