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 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 21 |
| 6 | 94 |
| 7 | 540 |
| 8 | 4207 |
| 9 | 42110 |
| 10 | 516344 |
| 11 | 7373924 |
| 12 | 118573592 |
| 13 | 2103205738 |
| 14 | 40634185402 |
| 15 | 847871397424 |
| 16 | 18987149095005 |
| 17 | 454032821688754 |
| 18 | 11544329612485981 |
| 19 | 310964453836198311 |
| 20 | 8845303172513781271 |