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 | 0 |
| 1 | 1 |
| 2 | 2112 |
| 3 | 266814 |
| 4 | 8396800 |
| 5 | 122109375 |
| 6 | 1088531136 |
| 7 | 6921055372 |
| 8 | 34360786944 |
| 9 | 141217159725 |
| 10 | 500005000000 |
| 11 | 1569223931946 |
| 12 | 4458068140032 |
| 13 | 11649073935499 |
| 14 | 28347008894400 |
| 15 | 64873254375000 |
| 16 | 140737622573056 |
| 17 | 291311323784217 |
| 18 | 578415996823104 |
| 19 | 1106657906468950 |
| 20 | 2048000640000000 |