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 | 0 |
| 4 | 4 |
| 5 | 0 |
| 6 | 0 |
| 7 | 70 |
| 8 | 560 |
| 9 | 0 |
| 10 | 5600 |
| 11 | 92400 |
| 12 | 369600 |
| 13 | 1201200 |
| 14 | 30830800 |
| 15 | 252252000 |
| 16 | 1210809600 |
| 17 | 19059040000 |
| 18 | 240143904000 |
| 19 | 1738184448000 |
| 20 | 22451549120000 |
| 21 | 342205063200000 |
| 22 | 3417705170880000 |
| 23 | 43866126368064000 |
| 24 | 732641268463104000 |
| 25 | 9234973972224000000 |