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 | 1 |
| 2 | 5 |
| 3 | 25 |
| 4 | 135 |
| 5 | 775 |
| 6 | 4651 |
| 7 | 28845 |
| 8 | 183450 |
| 9 | 1190050 |
| 10 | 7844230 |
| 11 | 52389678 |
| 12 | 353770190 |
| 13 | 2411324700 |
| 14 | 16568343325 |
| 15 | 114639216915 |
| 16 | 798076174113 |
| 17 | 5586035989185 |
| 18 | 39287407321075 |
| 19 | 277508001643575 |
| 20 | 1967816928168265 |
| 21 | 14003018984540741 |
| 22 | 99965175670335750 |