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 | 2 |
| 1 | 3 |
| 2 | 5 |
| 3 | 10 |
| 4 | 29 |
| 5 | 126 |
| 6 | 727 |
| 7 | 5048 |
| 8 | 40329 |
| 9 | 362890 |
| 10 | 3628811 |
| 11 | 39916812 |
| 12 | 479001613 |
| 13 | 6227020814 |
| 14 | 87178291215 |
| 15 | 1307674368016 |
| 16 | 20922789888017 |
| 17 | 355687428096018 |
| 18 | 6402373705728019 |
| 19 | 121645100408832020 |
| 20 | 2432902008176640021 |