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 | 120 |
| 2 | 540 |
| 3 | 2430 |
| 4 | 10242 |
| 5 | 44274 |
| 6 | 193194 |
| 7 | 835812 |
| 8 | 3617703 |
| 9 | 15692003 |
| 10 | 68014233 |
| 11 | 294705961 |
| 12 | 1277336862 |
| 13 | 5536267273 |
| 14 | 23993714457 |
| 15 | 103989408537 |
| 16 | 450697682809 |
| 17 | 1953337206374 |
| 18 | 8465825120096 |
| 19 | 36691243404754 |
| 20 | 159021259038334 |