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) |
|---|---|
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 16 |
| 6 | 48 |
| 7 | 140 |
| 8 | 428 |
| 9 | 1308 |
| 10 | 4072 |
| 11 | 12796 |
| 12 | 40432 |
| 13 | 129432 |
| 14 | 413900 |
| 15 | 1342580 |
| 16 | 4335288 |
| 17 | 14201804 |
| 18 | 46226896 |
| 19 | 152594276 |
| 20 | 500016036 |
| 21 | 1660630740 |
| 22 | 5472190206 |
| 23 | 18264517264 |
| 24 | 60475691308 |
| 25 | 202684618564 |
| 26 | 673892675030 |
| 27 | 2266436498400 |
| 28 | 7562707682032 |
| 29 | 25510762766704 |
| 30 | 85394319699916 |