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 | 2 |
| 2 | 6 |
| 3 | 34 |
| 4 | 250 |
| 5 | 972 |
| 6 | 15498 |
| 7 | 109544 |
| 8 | 5961306 |
| 9 | 54891535 |
| 10 | 2488870076 |
| 11 | 246264587430 |
| 12 | 118503860254 |
| 13 | 16917328320424 |
| 14 | 31020551370600 |
| 15 | 459016311081816 |
| 16 | 25084010473396186126 |
| 17 | 22789919291848918932 |
| 18 | 3423598216929042597 |
| 19 | 82480361346228654485320 |
| 20 | 12440086312584102532500 |
| 21 | 121292379506812780007192 |