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 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | -119 |
| 6 | -863 |
| 7 | -3527 |
| 8 | -10751 |
| 9 | -27215 |
| 10 | 7197121 |
| 11 | 96476689 |
| 12 | 689534209 |
| 13 | 3507486841 |
| 14 | 14238448225 |
| 15 | -5835497948279 |
| 16 | -114117547235327 |
| 17 | -1164586980639263 |
| 18 | -8296447373407871 |
| 19 | -46351121024513375 |
| 20 | 25734702161134932481 |
| 21 | 661538303263860440041 |