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 | 3 |
| 3 | 0 |
| 4 | 9 |
| 5 | 0 |
| 6 | -63 |
| 7 | 189 |
| 8 | 0 |
| 9 | -1944 |
| 10 | 6399 |
| 11 | 0 |
| 12 | -72009 |
| 13 | 245430 |
| 14 | 0 |
| 15 | -2921832 |
| 16 | 10184130 |
| 17 | 0 |
| 18 | -125775585 |
| 19 | 445134690 |
| 20 | 0 |
| 21 | -5641620192 |
| 22 | 20188568790 |
| 23 | 0 |
| 24 | -260832419406 |
| 25 | 941254831539 |
| 26 | 0 |
| 27 | -12342425759136 |
| 28 | 44833549152825 |
| 29 | 0 |
| 30 | -594857401230510 |
| 31 | 2172276845159733 |
| 32 | 0 |