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 | 1 |
| 2 | 5 |
| 3 | 25 |
| 4 | 157 |
| 5 | 1101 |
| 6 | 9211 |
| 7 | 85513 |
| 8 | 900033 |
| 9 | 10402633 |
| 10 | 133059331 |
| 11 | 1836961941 |
| 12 | 27619253113 |
| 13 | 444584808253 |
| 14 | 7678546353843 |
| 15 | 140944884572521 |
| 16 | 2751833492404321 |
| 17 | 56691826303303953 |
| 18 | 1233793951629951043 |
| 19 | 28191548364561422173 |
| 20 | 676190806704598883241 |