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 | 0 |
| 1 | 1 |
| 2 | 10 |
| 3 | 78 |
| 4 | 568 |
| 5 | 4120 |
| 6 | 30864 |
| 7 | 244720 |
| 8 | 2088832 |
| 9 | 19389312 |
| 10 | 196514560 |
| 11 | 2173194496 |
| 12 | 26128665600 |
| 13 | 339890756608 |
| 14 | 4759410116608 |
| 15 | 71395178280960 |
| 16 | 1142340032364544 |
| 17 | 19419853564641280 |
| 18 | 349557673401188352 |
| 19 | 6641597100292636672 |
| 20 | 132831947503410872320 |
| 21 | 2789470920661372502016 |