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 | 1 |
| 2 | 10 |
| 3 | 120 |
| 4 | 1560 |
| 5 | 21216 |
| 6 | 297024 |
| 7 | 4243200 |
| 8 | 61526400 |
| 9 | 902387200 |
| 10 | 13355330560 |
| 11 | 199115837440 |
| 12 | 2986737561600 |
| 13 | 45030812467200 |
| 14 | 681895160217600 |
| 15 | 10364806435307520 |
| 16 | 158063298138439680 |
| 17 | 2417438677411430400 |
| 18 | 37067393053641932800 |
| 19 | 569667303771760230400 |
| 20 | 8772876478085107548160 |