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 | 4 |
| 1 | 4 |
| 2 | 25 |
| 3 | 123 |
| 4 | 626 |
| 5 | 3127 |
| 6 | 15623 |
| 7 | 78123 |
| 8 | 390623 |
| 9 | 1953122 |
| 10 | 9765627 |
| 11 | 48828127 |
| 12 | 244140623 |
| 13 | 1220703121 |
| 14 | 6103515629 |
| 15 | 30517578127 |
| 16 | 152587890617 |
| 17 | 762939453119 |
| 18 | 3814697265623 |
| 19 | 19073486328122 |
| 20 | 95367431640623 |