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 | 4 |
| 3 | 35 |
| 4 | 275 |
| 5 | 2206 |
| 6 | 18602 |
| 7 | 166191 |
| 8 | 1574415 |
| 9 | 15788974 |
| 10 | 167183914 |
| 11 | 1863967135 |
| 12 | 21822793215 |
| 13 | 267611755414 |
| 14 | 3429246890754 |
| 15 | 45819357151439 |
| 16 | 637076509210383 |
| 17 | 9200974953803310 |
| 18 | 137799616003035306 |