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 | 2 |
| 1 | 1 |
| 2 | 2 |
| 3 | -3 |
| 4 | 10 |
| 5 | -45 |
| 6 | 250 |
| 7 | -1645 |
| 8 | 12490 |
| 9 | -107415 |
| 10 | 1031690 |
| 11 | -10943955 |
| 12 | 127058690 |
| 13 | -1602400085 |
| 14 | 21812913650 |
| 15 | -318763741725 |
| 16 | 4977247397650 |
| 17 | -82695799908975 |
| 18 | 1456703469048850 |
| 19 | -27117356172328675 |
| 20 | 531930264143933050 |