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 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 18 |
| 5 | 89 |
| 6 | 523 |
| 7 | 3599 |
| 8 | 28342 |
| 9 | 251532 |
| 10 | 2483877 |
| 11 | 27012163 |
| 12 | 320769441 |
| 13 | 4129906549 |
| 14 | 57302453361 |
| 15 | 852373993744 |
| 16 | 13531437150692 |
| 17 | 228343001917932 |
| 18 | 4081631159283027 |
| 19 | 77040788131467135 |
| 20 | 1531185664112909315 |