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 | 75 |
| 4 | 375 |
| 5 | 1875 |
| 6 | 9375 |
| 7 | 46875 |
| 8 | 234375 |
| 9 | 1171875 |
| 10 | 5859375 |
| 11 | 29296875 |
| 12 | 146484375 |
| 13 | 732421875 |
| 14 | 3662109375 |
| 15 | 18310546875 |
| 16 | 91552734375 |
| 17 | 457763671875 |
| 18 | 2288818359375 |
| 19 | 11444091796875 |
| 20 | 57220458984375 |