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 | 10 |
| 3 | 2780 |
| 4 | 6631556521 |
| 5 | 71669271794142235712392433 |
| 6 | 78417479379491793666843945562521255790293292270929676484784808001 |