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 | 5 |
| 2 | 25 |
| 3 | 126 |
| 4 | 635 |
| 5 | 3200 |
| 6 | 16126 |
| 7 | 81265 |
| 8 | 409525 |
| 9 | 2063751 |
| 10 | 10400020 |
| 11 | 52409625 |
| 12 | 264111876 |
| 13 | 1330959400 |
| 14 | 6707206625 |
| 15 | 33800145001 |
| 16 | 170331684405 |
| 17 | 858365628650 |
| 18 | 4325628288251 |
| 19 | 21798473125660 |
| 20 | 109850731256950 |
| 21 | 553579284573001 |