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 | 1 |
| 3 | 1 |
| 4 | -2 |
| 5 | 3 |
| 6 | -7 |
| 7 | 22 |
| 8 | -71 |
| 9 | 231 |
| 10 | -794 |
| 11 | 2945 |
| 12 | -11679 |
| 13 | 48770 |
| 14 | -212823 |
| 15 | 969221 |
| 16 | -4605674 |
| 17 | 22802431 |
| 18 | -117322423 |
| 19 | 625743878 |
| 20 | -3452893503 |
| 21 | 19684083947 |
| 22 | -115787084242 |
| 23 | 701935339725 |
| 24 | -4380330298815 |
| 25 | 28105726916034 |
| 26 | -185229395693615 |
| 27 | 1252696143653513 |