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 | -5 |
| 3 | -7 |
| 4 | 1 |
| 5 | 839 |
| 6 | 4171 |
| 7 | 54305 |
| 8 | 102817 |
| 9 | -4303441 |
| 10 | -74521349 |
| 11 | -1595325271 |
| 12 | -20768141855 |
| 13 | -222701825737 |
| 14 | 1485790534411 |
| 15 | 65580347824529 |
| 16 | 2880129557707201 |
| 17 | 67631429234674655 |
| 18 | 1543424936566399867 |
| 19 | 23542870556917468889 |
| 20 | 119940955037901088321 |