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 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 24 |
| 7 | 28 |
| 8 | 128 |
| 9 | 252 |
| 10 | 720 |
| 11 | 1364 |
| 12 | 3384 |
| 13 | 6552 |
| 14 | 14644 |
| 15 | 29040 |
| 16 | 61568 |
| 17 | 122400 |
| 18 | 253284 |
| 19 | 504868 |
| 20 | 1028880 |
| 21 | 2054416 |
| 22 | 4150652 |
| 23 | 8294444 |
| 24 | 16682552 |
| 25 | 33349800 |
| 26 | 66902472 |
| 27 | 133775964 |
| 28 | 267991444 |
| 29 | 535920696 |
| 30 | 1072788624 |
| 31 | 2145452092 |