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 | 20 |
| 3 | 70 |
| 4 | 225 |
| 5 | 681 |
| 6 | 1970 |
| 7 | 5500 |
| 8 | 14920 |
| 9 | 39520 |
| 10 | 102592 |
| 11 | 261760 |
| 12 | 657920 |
| 13 | 1632000 |
| 14 | 4001280 |
| 15 | 9708544 |
| 16 | 23336960 |
| 17 | 55623680 |
| 18 | 131563520 |
| 19 | 309002240 |
| 20 | 721092608 |
| 21 | 1672806400 |
| 22 | 3859415040 |
| 23 | 8859156480 |
| 24 | 20240138240 |
| 25 | 46038777856 |
| 26 | 104291368960 |
| 27 | 235342397440 |
| 28 | 529153392640 |