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 | 1 |
| 1 | 15 |
| 2 | 135 |
| 3 | 920 |
| 4 | 5220 |
| 5 | 25893 |
| 6 | 115700 |
| 7 | 475065 |
| 8 | 1817910 |
| 9 | 6551390 |
| 10 | 22414314 |
| 11 | 73265580 |
| 12 | 229972855 |
| 13 | 696109950 |
| 14 | 2039031360 |
| 15 | 5796944357 |
| 16 | 16036186005 |
| 17 | 43259046975 |
| 18 | 114012183695 |
| 19 | 294067720380 |
| 20 | 743368453326 |
| 21 | 1844121021245 |
| 22 | 4494803760045 |