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 | -2 |
| 3 | -3 |
| 4 | -3 |
| 5 | 40 |
| 6 | 477 |
| 7 | 4375 |
| 8 | 45154 |
| 9 | 486817 |
| 10 | 5002397 |
| 11 | 54970652 |
| 12 | 732601449 |
| 13 | 10046371231 |
| 14 | 113632306694 |
| 15 | 1051655108629 |
| 16 | 12585372336141 |
| 17 | 202763995934160 |
| 18 | -863641466773595 |
| 19 | -247388278229558697 |
| 20 | -10810815349601723990 |
| 21 | -311011007642247422759 |