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 | 3 |
| 2 | 15 |
| 3 | 220 |
| 4 | 7315 |
| 5 | 435897 |
| 6 | 40475358 |
| 7 | 5373200880 |
| 8 | 962889794295 |
| 9 | 223581013518060 |
| 10 | 65230517839369311 |
| 11 | 23345156728397937888 |
| 12 | 10052806195411162278095 |
| 13 | 5126493560257678027274800 |