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 | 4 |
| 2 | 12 |
| 3 | 41 |
| 4 | 159 |
| 5 | 685 |
| 6 | 3232 |
| 7 | 16497 |
| 8 | 90075 |
| 9 | 520248 |
| 10 | 3143900 |
| 11 | 19678699 |
| 12 | 126480319 |
| 13 | 828889655 |
| 14 | 5508880129 |
| 15 | 36980189248 |
| 16 | 249999755818 |
| 17 | 1698491520413 |
| 18 | 11579658486155 |
| 19 | 79137696973965 |
| 20 | 541762392142995 |
| 21 | 3713215153801152 |