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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | -1 |
| 5 | 2 |
| 6 | -5 |
| 7 | 21 |
| 8 | -109 |
| 9 | 671 |
| 10 | -4772 |
| 11 | 38591 |
| 12 | -350036 |
| 13 | 3520830 |
| 14 | -38903271 |
| 15 | 468490350 |
| 16 | -6107642906 |
| 17 | 85704534787 |
| 18 | -1288021805215 |
| 19 | 20641247413120 |
| 20 | -351374756822383 |
| 21 | 6332030169529731 |
| 22 | -120427840368046909 |
| 23 | 2410627702030000447 |
| 24 | -50661193580285096086 |