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 | 9 |
| 4 | 25 |
| 5 | 25 |
| 6 | -429 |
| 7 | -4151 |
| 8 | -8175 |
| 9 | 320625 |
| 10 | 5241475 |
| 11 | 23329801 |
| 12 | -705579159 |
| 13 | -18521117303 |
| 14 | -150119840493 |
| 15 | 3366485315145 |
| 16 | 138253031778721 |
| 17 | 1780881865542625 |
| 18 | -28047359274759549 |
| 19 | -1854674541474191351 |
| 20 | -34985197604145203655 |
| 21 | 332608115115937927161 |