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 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 51 |
| 5 | 201 |
| 6 | 813 |
| 7 | 3333 |
| 8 | 13779 |
| 9 | 57361 |
| 10 | 240153 |
| 11 | 1010109 |
| 12 | 4264989 |
| 13 | 18066777 |
| 14 | 76745763 |
| 15 | 326796213 |
| 16 | 1394494803 |
| 17 | 5961639969 |
| 18 | 25528971369 |
| 19 | 109482236013 |
| 20 | 470145451401 |
| 21 | 2021360463849 |
| 22 | 8700225608583 |
| 23 | 37484437325157 |
| 24 | 161647475666301 |
| 25 | 697673760945201 |