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 | 0 |
| 2 | 3 |
| 3 | 20 |
| 4 | 139 |
| 5 | 1069 |
| 6 | 8747 |
| 7 | 74114 |
| 8 | 641594 |
| 9 | 5661135 |
| 10 | 50653546 |
| 11 | 458352691 |
| 12 | 4185483176 |
| 13 | 38510936699 |
| 14 | 356622729564 |
| 15 | 3320632228693 |
| 16 | 31067060521057 |
| 17 | 291869049531878 |
| 18 | 2752144407792176 |
| 19 | 26035873192178041 |
| 20 | 247025281876786013 |
| 21 | 2349914303292170310 |
| 22 | 22407593754131275705 |