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 | 0 |
| 2 | 3 |
| 3 | 12 |
| 4 | 39 |
| 5 | 120 |
| 6 | 363 |
| 7 | 1092 |
| 8 | 3279 |
| 9 | 9840 |
| 10 | 29523 |
| 11 | 88572 |
| 12 | 265719 |
| 13 | 797160 |
| 14 | 2391483 |
| 15 | 7174452 |
| 16 | 21523359 |
| 17 | 64570080 |
| 18 | 193710243 |
| 19 | 581130732 |
| 20 | 1743392199 |
| 21 | 5230176600 |
| 22 | 15690529803 |
| 23 | 47071589412 |
| 24 | 141214768239 |