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 | 1 |
| 3 | 5 |
| 4 | 25 |
| 5 | 135 |
| 6 | 675 |
| 7 | 3475 |
| 8 | 17375 |
| 9 | 87385 |
| 10 | 437175 |
| 11 | 2188575 |
| 12 | 10942875 |
| 13 | 54730525 |
| 14 | 273652625 |
| 15 | 1368332625 |
| 16 | 6841676625 |
| 17 | 34208737630 |
| 18 | 171043688150 |
| 19 | 855220256700 |
| 20 | 4276101283500 |
| 21 | 21380515232550 |
| 22 | 106902576510250 |
| 23 | 534512926322750 |