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 | 5 |
| 2 | 15 |
| 3 | 75 |
| 4 | 495 |
| 5 | 3600 |
| 6 | 28275 |
| 7 | 232500 |
| 8 | 1979385 |
| 9 | 17287050 |
| 10 | 154041450 |
| 11 | 1394844375 |
| 12 | 12797919900 |
| 13 | 118722187125 |
| 14 | 1111672312125 |
| 15 | 10493033896875 |
| 16 | 99734572903680 |
| 17 | 953755379940150 |
| 18 | 9169941599036475 |
| 19 | 88588446263805000 |
| 20 | 859511126918229075 |
| 21 | 8371534717621838250 |