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 | 0 |
| 2 | 2 |
| 3 | 9 |
| 4 | 41 |
| 5 | 189 |
| 6 | 880 |
| 7 | 4131 |
| 8 | 19522 |
| 9 | 92763 |
| 10 | 442798 |
| 11 | 2121795 |
| 12 | 10200477 |
| 13 | 49176639 |
| 14 | 237661176 |
| 15 | 1151032005 |
| 16 | 5585185425 |
| 17 | 27146751885 |
| 18 | 132145210270 |
| 19 | 644128990155 |
| 20 | 3143590707235 |
| 21 | 15358979381175 |
| 22 | 75117256339240 |
| 23 | 367723284610905 |