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) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 2 |
| 4 | 4 |
| 5 | 17 |
| 6 | 28 |
| 7 | 189 |
| 8 | 531 |
| 9 | 1990 |
| 10 | 5747 |
| 11 | 23902 |
| 12 | 76658 |
| 13 | 291478 |
| 14 | 982793 |
| 15 | 3677580 |
| 16 | 13214719 |
| 17 | 49161612 |
| 18 | 177190667 |
| 19 | 664806798 |
| 20 | 2443387945 |