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) |
|---|---|
| 4 | 1 |
| 5 | 5 |
| 6 | 20 |
| 7 | 70 |
| 8 | 230 |
| 9 | 726 |
| 10 | 2235 |
| 11 | 6765 |
| 12 | 20240 |
| 13 | 60060 |
| 14 | 177177 |
| 15 | 520455 |
| 16 | 1524120 |
| 17 | 4453320 |
| 18 | 12991230 |
| 19 | 37854954 |
| 20 | 110218905 |
| 21 | 320751445 |
| 22 | 933149470 |
| 23 | 2714401580 |
| 24 | 7895719634 |
| 25 | 22969224850 |
| 26 | 66829893650 |
| 27 | 194486929650 |
| 28 | 566141346225 |
| 29 | 1648500576021 |