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 | -4 |
| 3 | 11 |
| 4 | 21 |
| 5 | -674 |
| 6 | 6551 |
| 7 | -33479 |
| 8 | -174114 |
| 9 | 7478121 |
| 10 | -117699599 |
| 11 | 1090997976 |
| 12 | 865365421 |
| 13 | -302755297739 |
| 14 | 7922094623596 |
| 15 | -127940743443649 |
| 16 | 974028543402401 |
| 17 | 21377262410290446 |
| 18 | -1179125036786673989 |
| 19 | 31760741865879345821 |
| 20 | -552216474702144564074 |
| 21 | 2814873629049018241701 |