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 | -11 |
| 4 | -41 |
| 5 | -75 |
| 6 | 1540 |
| 7 | 37725 |
| 8 | 657715 |
| 9 | 10551750 |
| 10 | 163089430 |
| 11 | 2407275470 |
| 12 | 31865298262 |
| 13 | 290682880132 |
| 14 | -2479867505029 |
| 15 | -267542605513289 |
| 16 | -11438897571729494 |
| 17 | -404343336811199242 |
| 18 | -13192591498632627584 |
| 19 | -410340915410006575406 |
| 20 | -12233989907129223814578 |