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 | 0 |
| 2 | -1512 |
| 3 | 44352 |
| 4 | 449064 |
| 5 | 6519744 |
| 6 | 47263608 |
| 7 | 257027904 |
| 8 | 1115041032 |
| 9 | 4093040448 |
| 10 | 13000566096 |
| 11 | 37057027392 |
| 12 | 96945887304 |
| 13 | 232758852480 |
| 14 | 526296318912 |
| 15 | 1128198915648 |
| 16 | 2286101175624 |
| 17 | 4451375005056 |
| 18 | 8386154766360 |
| 19 | 15131349955008 |
| 20 | 26614555499952 |