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) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | -4 |
| 5 | 29 |
| 6 | -124 |
| 7 | 1583 |
| 8 | -17088 |
| 9 | 124553 |
| 10 | -1152816 |
| 11 | 20127867 |
| 12 | -262838016 |
| 13 | 3978820221 |
| 14 | -48595514304 |
| 15 | 914656587063 |
| 16 | -24441484099584 |
| 17 | 370244721585681 |
| 18 | -5884988565575424 |
| 19 | 162968423791332339 |
| 20 | -3855257807841017856 |
| 21 | 82014901819948738629 |
| 22 | -1934570487417807744000 |
| 23 | 58311771938510122952559 |