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 | 1 |
| 2 | 6 |
| 3 | 15 |
| 4 | 44 |
| 5 | 205 |
| 6 | 1218 |
| 7 | 8547 |
| 8 | 68440 |
| 9 | 615897 |
| 10 | 6158910 |
| 11 | 67747911 |
| 12 | 812974980 |
| 13 | 10568674805 |
| 14 | 147961447354 |
| 15 | 2219421710235 |
| 16 | 35510747363504 |
| 17 | 603682705179313 |
| 18 | 10866288693227382 |
| 19 | 206459485171319935 |
| 20 | 4129189703426398300 |
| 21 | 86712983771954363901 |