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 | 0 |
| 2 | 1 |
| 3 | 30 |
| 4 | 600 |
| 5 | 10000 |
| 6 | 150000 |
| 7 | 2100000 |
| 8 | 28000000 |
| 9 | 360000000 |
| 10 | 4500000000 |
| 11 | 55000000000 |
| 12 | 660000000000 |
| 13 | 7800000000000 |
| 14 | 91000000000000 |
| 15 | 1050000000000000 |
| 16 | 12000000000000000 |
| 17 | 136000000000000000 |
| 18 | 1530000000000000000 |