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 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 45 |
| 4 | 225 |
| 5 | 675 |
| 6 | 3375 |
| 7 | 10125 |
| 8 | 50625 |
| 9 | 151875 |
| 10 | 759375 |
| 11 | 2278125 |
| 12 | 11390625 |
| 13 | 34171875 |
| 14 | 170859375 |
| 15 | 512578125 |
| 16 | 2562890625 |
| 17 | 7688671875 |
| 18 | 38443359375 |
| 19 | 115330078125 |
| 20 | 576650390625 |
| 21 | 1729951171875 |
| 22 | 8649755859375 |
| 23 | 25949267578125 |