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 | 20 |
| 2 | 250 |
| 3 | 2400 |
| 4 | 19375 |
| 5 | 137604 |
| 6 | 884430 |
| 7 | 5241000 |
| 8 | 29017815 |
| 9 | 151597440 |
| 10 | 752997538 |
| 11 | 3577442200 |
| 12 | 16335561280 |
| 13 | 71979549460 |
| 14 | 307075300540 |
| 15 | 1271938667704 |
| 16 | 5127690095315 |
| 17 | 20161295885120 |
| 18 | 77454572685460 |