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 | -3 |
| 3 | -7 |
| 4 | -15 |
| 5 | 89 |
| 6 | 1737 |
| 7 | 21713 |
| 8 | 266865 |
| 9 | 3162089 |
| 10 | 34737177 |
| 11 | 352100033 |
| 12 | 2848598145 |
| 13 | -7655375911 |
| 14 | -1359369828183 |
| 15 | -50221626404047 |
| 16 | -1460912626424175 |
| 17 | -39804558811289911 |
| 18 | -1080962878982246343 |
| 19 | -29431779044695154527 |
| 20 | -788320672341728128095 |
| 21 | -20386762121171790275911 |