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 | 1 |
| 2 | 4 |
| 3 | 18 |
| 4 | 76 |
| 5 | 315 |
| 6 | 1296 |
| 7 | 5320 |
| 8 | 21800 |
| 9 | 89190 |
| 10 | 364460 |
| 11 | 1487948 |
| 12 | 6070332 |
| 13 | 24750570 |
| 14 | 100868236 |
| 15 | 410919990 |
| 16 | 1673486992 |
| 17 | 6813529348 |
| 18 | 27734769756 |
| 19 | 112874034844 |
| 20 | 459295593200 |
| 21 | 1868653768443 |
| 22 | 7601716598916 |
| 23 | 30920563717052 |
| 24 | 125759730486432 |
| 25 | 511445050400275 |
| 26 | 2079809585544808 |
| 27 | 8457048866652588 |
| 28 | 34386482811155244 |