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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | -1 |
| 4 | -2 |
| 5 | 9 |
| 6 | 6 |
| 7 | -155 |
| 8 | 232 |
| 9 | 3969 |
| 10 | -20870 |
| 11 | -118779 |
| 12 | 1655028 |
| 13 | 1610257 |
| 14 | -143697722 |
| 15 | 522358005 |
| 16 | 13332842416 |
| 17 | -138189937791 |
| 18 | -1128293525646 |
| 19 | 29219838555781 |
| 20 | 17274118159180 |
| 21 | -5993074252801839 |
| 22 | 38541972209299966 |
| 23 | 1179892974640047669 |