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) |
|---|---|
| 1 | 3 |
| 2 | 15 |
| 3 | 57 |
| 4 | 223 |
| 5 | 863 |
| 6 | 3333 |
| 7 | 12883 |
| 8 | 49791 |
| 9 | 192441 |
| 10 | 743775 |
| 11 | 2874655 |
| 12 | 11110405 |
| 13 | 42941187 |
| 14 | 165965647 |
| 15 | 641449337 |
| 16 | 2479171199 |
| 17 | 9581878847 |
| 18 | 37033506309 |
| 19 | 143132741651 |
| 20 | 553201243263 |
| 21 | 2138096511097 |
| 22 | 8263641389887 |
| 23 | 31938581194175 |
| 24 | 123441098248197 |
| 25 | 477093977471363 |
| 26 | 1843945546253839 |
| 27 | 7126761892007865 |