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 | 1 |
| 2 | 5 |
| 3 | 25 |
| 4 | 145 |
| 5 | 1025 |
| 6 | 8245 |
| 7 | 72745 |
| 8 | 704705 |
| 9 | 7424065 |
| 10 | 83940805 |
| 11 | 1012504505 |
| 12 | 12972555025 |
| 13 | 175624847425 |
| 14 | 2501468566325 |
| 15 | 37364323364425 |
| 16 | 583569693556225 |
| 17 | 9504040277271425 |
| 18 | 161021013457176325 |
| 19 | 2832196631069755225 |
| 20 | 51619359912771959825 |