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 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 40 |
| 5 | 184 |
| 6 | 720 |
| 7 | 3072 |
| 8 | 12544 |
| 9 | 52416 |
| 10 | 216448 |
| 11 | 899328 |
| 12 | 3724800 |
| 13 | 15452672 |
| 14 | 64052224 |
| 15 | 265617408 |
| 16 | 1101234176 |
| 17 | 4566192128 |
| 18 | 18932244480 |
| 19 | 78498938880 |
| 20 | 325475532800 |
| 21 | 1349511512064 |
| 22 | 5595423113216 |
| 23 | 23200121487360 |
| 24 | 96193798471680 |
| 25 | 398845002121216 |