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 | 4 |
| 2 | 18 |
| 3 | 86 |
| 4 | 424 |
| 5 | 2128 |
| 6 | 10798 |
| 7 | 55190 |
| 8 | 283510 |
| 9 | 1461730 |
| 10 | 7557166 |
| 11 | 39153338 |
| 12 | 203188892 |
| 13 | 1055863564 |
| 14 | 5492668906 |
| 15 | 28598497610 |
| 16 | 149012237696 |
| 17 | 776904940576 |
| 18 | 4052654604042 |
| 19 | 21149661562298 |
| 20 | 110415949871240 |
| 21 | 576636302495488 |