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 | 2 |
| 3 | 5 |
| 4 | 14 |
| 5 | 42 |
| 6 | 132 |
| 7 | 428 |
| 8 | 1420 |
| 9 | 4796 |
| 10 | 16432 |
| 11 | 56966 |
| 12 | 199444 |
| 13 | 704146 |
| 14 | 2504000 |
| 15 | 8960445 |
| 16 | 32241670 |
| 17 | 116580200 |
| 18 | 423372684 |
| 19 | 1543542369 |
| 20 | 5647383786 |
| 21 | 20728481590 |
| 22 | 76305607480 |
| 23 | 281648344965 |
| 24 | 1042139463066 |
| 25 | 3864822037106 |
| 26 | 14362983740692 |
| 27 | 53481776523398 |