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) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 21 |
| 4 | 124 |
| 5 | 825 |
| 6 | 6186 |
| 7 | 51961 |
| 8 | 484968 |
| 9 | 4988241 |
| 10 | 56117710 |
| 11 | 685883121 |
| 12 | 9053657196 |
| 13 | 128397320233 |
| 14 | 1947359356866 |
| 15 | 31457343457065 |
| 16 | 539268744978256 |
| 17 | 9778739908939041 |
| 18 | 187018400758459158 |
| 19 | 3762370179964296001 |
| 20 | 79427814910357360020 |
| 21 | 1755772750650004800441 |