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 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 6 |
| 5 | 0 |
| 6 | 0 |
| 7 | 2196 |
| 8 | 37004 |
| 9 | 0 |
| 10 | 0 |
| 11 | 2317631400 |
| 12 | 216893681800 |
| 13 | 0 |
| 14 | 0 |
| 15 | 2326335506123418128 |
| 16 | 1208982377794384163088 |
| 17 | 0 |
| 18 | 0 |
| 19 | 2220650888749669503773432361504 |
| 20 | 6408743336016148761893699822360672 |
| 21 | 0 |
| 22 | 0 |
| 23 | 2015895925780490675949731718780144934779733312 |