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 | -1 |
| 4 | 4 |
| 5 | -21 |
| 6 | 133 |
| 7 | -981 |
| 8 | 8244 |
| 9 | -77694 |
| 10 | 811194 |
| 11 | -9292075 |
| 12 | 115843000 |
| 13 | -1561272571 |
| 14 | 22618147199 |
| 15 | -350481556959 |
| 16 | 5784147674772 |
| 17 | -101284047800632 |
| 18 | 1875504207906184 |
| 19 | -36616289396963678 |
| 20 | 751702523788615816 |
| 21 | -16187581390548113842 |
| 22 | 364861626149143519378 |
| 23 | -8590429045711448354359 |