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 | 3 |
| 3 | 7 |
| 4 | 19 |
| 5 | 45 |
| 6 | 123 |
| 7 | 285 |
| 8 | 807 |
| 9 | 1771 |
| 10 | 5407 |
| 11 | 10587 |
| 12 | 37627 |
| 13 | 57619 |
| 14 | 279783 |
| 15 | 231615 |
| 16 | 2307339 |
| 17 | -387531 |
| 18 | 21769251 |
| 19 | -28249347 |
| 20 | 235837791 |
| 21 | -539858235 |
| 22 | 2857845723 |
| 23 | -8509970007 |
| 24 | 37342507167 |
| 25 | -126289733319 |
| 26 | 510715973643 |
| 27 | -1837291760147 |