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 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 56 |
| 5 | 280 |
| 6 | 1452 |
| 7 | 7700 |
| 8 | 41456 |
| 9 | 225648 |
| 10 | 1238420 |
| 11 | 6840988 |
| 12 | 37986984 |
| 13 | 211842696 |
| 14 | 1185635388 |
| 15 | 6655993380 |
| 16 | 37463920608 |
| 17 | 211350457824 |
| 18 | 1194706644516 |
| 19 | 6765300359468 |
| 20 | 38370431711000 |
| 21 | 217931108199672 |