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 | 21 |
| 3 | 171 |
| 4 | 1521 |
| 5 | 14283 |
| 6 | 138909 |
| 7 | 1385163 |
| 8 | 14072193 |
| 9 | 145039923 |
| 10 | 1512191781 |
| 11 | 15914734443 |
| 12 | 168802010001 |
| 13 | 1802247516891 |
| 14 | 19350710547021 |
| 15 | 208783189719531 |
| 16 | 2262263134211073 |
| 17 | 24604815145831011 |
| 18 | 268499713118585781 |
| 19 | 2938736789722114731 |
| 20 | 32250788066104022961 |