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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 20 |
| 6 | 80 |
| 7 | 336 |
| 8 | 1344 |
| 9 | 5440 |
| 10 | 21760 |
| 11 | 87296 |
| 12 | 349184 |
| 13 | 1397760 |
| 14 | 5591040 |
| 15 | 22368256 |
| 16 | 89473024 |
| 17 | 357908480 |
| 18 | 1431633920 |
| 19 | 5726601216 |
| 20 | 22906404864 |
| 21 | 91625881600 |
| 22 | 366503526400 |
| 23 | 1466015154176 |
| 24 | 5864060616704 |
| 25 | 23456246661120 |
| 26 | 93824986644480 |
| 27 | 375299963355136 |
| 28 | 1501199853420544 |
| 29 | 6004799480791040 |