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 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 20 |
| 5 | 250 |
| 6 | 2500 |
| 7 | 21875 |
| 8 | 175000 |
| 9 | 1312500 |
| 10 | 9375000 |
| 11 | 64453125 |
| 12 | 429687500 |
| 13 | 2792968750 |
| 14 | 17773437500 |
| 15 | 111083984375 |
| 16 | 683593750000 |
| 17 | 4150390625000 |
| 18 | 24902343750000 |
| 19 | 147857666015625 |
| 20 | 869750976562500 |
| 21 | 5073547363281250 |