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 | 120 |
| 2 | 4950 |
| 3 | 108900 |
| 4 | 1557270 |
| 5 | 16195608 |
| 6 | 131589315 |
| 7 | 877262100 |
| 8 | 4971151900 |
| 9 | 24584605760 |
| 10 | 108284013552 |
| 11 | 431621592480 |
| 12 | 1577078895600 |
| 13 | 5337805492800 |
| 14 | 16880809870980 |
| 15 | 50245234086564 |
| 16 | 141622596077325 |
| 17 | 379998709805000 |
| 18 | 974996689631250 |
| 19 | 2401570793407500 |