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 | 13 |
| 3 | 63 |
| 4 | 313 |
| 5 | 1563 |
| 6 | 7813 |
| 7 | 39063 |
| 8 | 195313 |
| 9 | 976563 |
| 10 | 4882813 |
| 11 | 24414063 |
| 12 | 122070313 |
| 13 | 610351563 |
| 14 | 3051757813 |
| 15 | 15258789063 |
| 16 | 76293945313 |
| 17 | 381469726563 |
| 18 | 1907348632813 |
| 19 | 9536743164063 |
| 20 | 47683715820313 |
| 21 | 238418579101563 |