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 | 2 |
| 2 | -5 |
| 3 | 30 |
| 4 | -215 |
| 5 | 1710 |
| 6 | -14516 |
| 7 | 128830 |
| 8 | -1180920 |
| 9 | 11093830 |
| 10 | -106245975 |
| 11 | 1033454774 |
| 12 | -10181848705 |
| 13 | 101394979530 |
| 14 | -1018972470275 |
| 15 | 10320779179380 |
| 16 | -105250097458410 |
| 17 | 1079767027094630 |
| 18 | -11136159773691830 |
| 19 | 115395278542757580 |
| 20 | -1200814926210284360 |