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 | 2 |
| 2 | -8 |
| 3 | 72 |
| 4 | -768 |
| 5 | 9072 |
| 6 | -114240 |
| 7 | 1502976 |
| 8 | -20414208 |
| 9 | 284083968 |
| 10 | -4029438976 |
| 11 | 58040074752 |
| 12 | -846682968064 |
| 13 | 12483389708288 |
| 14 | -185725854932992 |
| 15 | 2784798982701056 |
| 16 | -42039464045854720 |
| 17 | 638415031298588672 |
| 18 | -9746180768647217152 |
| 19 | 149486708349609050112 |