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 | 0 |
| 1 | 3 |
| 2 | 18 |
| 3 | 81 |
| 4 | 324 |
| 5 | 1215 |
| 6 | 4374 |
| 7 | 15309 |
| 8 | 52488 |
| 9 | 177147 |
| 10 | 590490 |
| 11 | 1948617 |
| 12 | 6377292 |
| 13 | 20726199 |
| 14 | 66961566 |
| 15 | 215233605 |
| 16 | 688747536 |
| 17 | 2195382771 |
| 18 | 6973568802 |
| 19 | 22082967873 |
| 20 | 69735688020 |
| 21 | 219667417263 |
| 22 | 690383311398 |
| 23 | 2165293113021 |
| 24 | 6778308875544 |
| 25 | 21182215236075 |
| 26 | 66088511536554 |
| 27 | 205891132094649 |