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 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 6 |
| 5 | 20 |
| 6 | 80 |
| 7 | 350 |
| 8 | 1750 |
| 9 | 10080 |
| 10 | 64512 |
| 11 | 450912 |
| 12 | 3438204 |
| 13 | 28471872 |
| 14 | 253913088 |
| 15 | 2424193200 |
| 16 | 24687555750 |
| 17 | 267199961600 |
| 18 | 3062092267520 |
| 19 | 37037541651968 |
| 20 | 471565937953396 |
| 21 | 6304419553216512 |
| 22 | 88298062293762048 |
| 23 | 1292879475255280640 |
| 24 | 19753693667117055100 |