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 | -3 |
| 2 | -9 |
| 3 | -45 |
| 4 | -270 |
| 5 | -1782 |
| 6 | -12474 |
| 7 | -90882 |
| 8 | -681615 |
| 9 | -5225715 |
| 10 | -40760577 |
| 11 | -322379109 |
| 12 | -2579032872 |
| 13 | -20830650120 |
| 14 | -169621008120 |
| 15 | -1390892266584 |
| 16 | -11474861199318 |
| 17 | -95173848770814 |
| 18 | -793115406423450 |
| 19 | -6637123664280450 |
| 20 | -55751838779955780 |