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 | 3 |
| 2 | 15 |
| 3 | 65 |
| 4 | 325 |
| 5 | 1575 |
| 6 | 7875 |
| 7 | 39125 |
| 8 | 195625 |
| 9 | 976875 |
| 10 | 4884375 |
| 11 | 24415625 |
| 12 | 122078125 |
| 13 | 610359375 |
| 14 | 3051796875 |
| 15 | 15258828125 |
| 16 | 76294140625 |
| 17 | 381469921875 |
| 18 | 1907349609375 |
| 19 | 9536744140625 |
| 20 | 47683720703125 |