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 | 9 |
| 2 | 540 |
| 3 | 19755 |
| 4 | 262296 |
| 5 | 1953405 |
| 6 | 10078164 |
| 7 | 40354335 |
| 8 | 134218800 |
| 9 | 387422001 |
| 10 | 1000002060 |
| 11 | 2357950419 |
| 12 | 5159783880 |
| 13 | 10604503845 |
| 14 | 20661052356 |
| 15 | 38443366215 |
| 16 | 68719485024 |
| 17 | 118587886425 |
| 18 | 198359302140 |
| 19 | 322687711611 |
| 20 | 512000016120 |