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 | 9 |
| 3 | 39 |
| 4 | 121 |
| 5 | 443 |
| 6 | 1521 |
| 7 | 5071 |
| 8 | 17161 |
| 9 | 58035 |
| 10 | 196249 |
| 11 | 664183 |
| 12 | 2247001 |
| 13 | 7601259 |
| 14 | 25715041 |
| 15 | 86992799 |
| 16 | 294294025 |
| 17 | 995591267 |
| 18 | 3368061225 |
| 19 | 11394069191 |
| 20 | 38545861561 |
| 21 | 130399710235 |
| 22 | 441139057489 |
| 23 | 1492362749807 |
| 24 | 5048627017225 |
| 25 | 17079382868243 |
| 26 | 57779138385081 |
| 27 | 195465425009943 |