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 | 2 |
| 5 | 8 |
| 6 | 32 |
| 7 | 112 |
| 8 | 412 |
| 9 | 1504 |
| 10 | 5760 |
| 11 | 22464 |
| 12 | 91224 |
| 13 | 379424 |
| 14 | 1632896 |
| 15 | 7201472 |
| 16 | 32709136 |
| 17 | 152094976 |
| 18 | 725810176 |
| 19 | 3540883968 |
| 20 | 17680145184 |
| 21 | 90115509888 |
| 22 | 469094763008 |
| 23 | 2489169367808 |
| 24 | 13465672180160 |
| 25 | 74161734785536 |