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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | -1 |
| 4 | 4 |
| 5 | -29 |
| 6 | 309 |
| 7 | -4383 |
| 8 | 78121 |
| 9 | -1684706 |
| 10 | 42801222 |
| 11 | -1255919755 |
| 12 | 41918624013 |
| 13 | -1572257236114 |
| 14 | 65619165625383 |
| 15 | -3022617826829288 |
| 16 | 152615633802149416 |
| 17 | -8397224009015443509 |
| 18 | 500957609480739613321 |