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 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 5040 |
| 8 | 38880 |
| 9 | 323520 |
| 10 | 2953728 |
| 11 | 29666304 |
| 12 | 326584320 |
| 13 | 3919011840 |
| 14 | 50969640960 |
| 15 | 705722941440 |
| 16 | 10504707686400 |
| 17 | 167258901086208 |
| 18 | 2836455721721856 |
| 19 | 51038126752727040 |
| 20 | 971132188892405760 |