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 | 15 |
| 3 | 63 |
| 4 | 243 |
| 5 | 891 |
| 6 | 3159 |
| 7 | 10935 |
| 8 | 37179 |
| 9 | 124659 |
| 10 | 413343 |
| 11 | 1358127 |
| 12 | 4428675 |
| 13 | 14348907 |
| 14 | 46235367 |
| 15 | 148272039 |
| 16 | 473513931 |
| 17 | 1506635235 |
| 18 | 4778186031 |
| 19 | 15109399071 |
| 20 | 47652720147 |
| 21 | 149931729243 |
| 22 | 470715894135 |
| 23 | 1474909801623 |
| 24 | 4613015762523 |
| 25 | 14403906360531 |
| 26 | 44906296300479 |