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 | -2 |
| 2 | 1 |
| 3 | -9 |
| 4 | 15 |
| 5 | -50 |
| 6 | 118 |
| 7 | -324 |
| 8 | 831 |
| 9 | -2195 |
| 10 | 5725 |
| 11 | -15012 |
| 12 | 39276 |
| 13 | -102854 |
| 14 | 269245 |
| 15 | -704925 |
| 16 | 1845483 |
| 17 | -4831574 |
| 18 | 12649186 |
| 19 | -33116040 |
| 20 | 86698875 |
| 21 | -226980647 |
| 22 | 594243001 |
| 23 | -1555748424 |
| 24 | 4073002200 |
| 25 | -10663258250 |
| 26 | 27916772473 |
| 27 | -73087059249 |
| 28 | 191344405191 |