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 | 6 |
| 2 | 21 |
| 3 | 126 |
| 4 | 666 |
| 5 | 3996 |
| 6 | 23436 |
| 7 | 140616 |
| 8 | 840456 |
| 9 | 5042736 |
| 10 | 30236976 |
| 11 | 181421856 |
| 12 | 1088414496 |
| 13 | 6530486976 |
| 14 | 39182222016 |
| 15 | 235093332096 |
| 16 | 1410555793536 |
| 17 | 8463334761216 |
| 18 | 50779983373056 |
| 19 | 304679900238336 |
| 20 | 1828079250264576 |
| 21 | 10968475501587456 |
| 22 | 65810852102532096 |