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) |
|---|---|
| 2 | 2 |
| 3 | 2 |
| 4 | 8 |
| 5 | 20 |
| 6 | 60 |
| 7 | 170 |
| 8 | 492 |
| 9 | 1414 |
| 10 | 4074 |
| 11 | 11728 |
| 12 | 33772 |
| 13 | 97240 |
| 14 | 279994 |
| 15 | 806208 |
| 16 | 2321386 |
| 17 | 6684162 |
| 18 | 19246280 |
| 19 | 55417452 |
| 20 | 159568196 |
| 21 | 459458306 |
| 22 | 1322957468 |
| 23 | 3809304206 |
| 24 | 10968454314 |
| 25 | 31582405472 |
| 26 | 90937912212 |
| 27 | 261845282320 |
| 28 | 753953441490 |