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 | 3 |
| 2 | 12 |
| 3 | 50 |
| 4 | 210 |
| 5 | 882 |
| 6 | 3696 |
| 7 | 15444 |
| 8 | 64350 |
| 9 | 267410 |
| 10 | 1108536 |
| 11 | 4585308 |
| 12 | 18929092 |
| 13 | 78004500 |
| 14 | 320932800 |
| 15 | 1318498920 |
| 16 | 5409723510 |
| 17 | 22169259090 |
| 18 | 90751353000 |
| 19 | 371125269900 |
| 20 | 1516311817020 |
| 21 | 6189965556060 |
| 22 | 25249187564640 |
| 23 | 102917884095000 |
| 24 | 419218847880300 |
| 25 | 1706543186909652 |