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 | 10 |
| 4 | -15 |
| 5 | -474 |
| 6 | 12565 |
| 7 | -258572 |
| 8 | 5136705 |
| 9 | -102255290 |
| 10 | 2019481101 |
| 11 | -37521627252 |
| 12 | 543274535089 |
| 13 | 1220679586140 |
| 14 | -663297992874075 |
| 15 | 45545891767647976 |
| 16 | -2512550066073884415 |
| 17 | 129402386434475858502 |
| 18 | -6511375580923238310755 |
| 19 | 325739815788711661063900 |