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 | 429 |
| 8 | 1430 |
| 9 | 4861 |
| 10 | 16785 |
| 11 | 58708 |
| 12 | 207557 |
| 13 | 740520 |
| 14 | 2662812 |
| 15 | 9640581 |
| 16 | 35112513 |
| 17 | 128563215 |
| 18 | 472951884 |
| 19 | 1747233370 |
| 20 | 6479450415 |
| 21 | 24111470952 |
| 22 | 90006390290 |
| 23 | 336953657070 |
| 24 | 1264770431964 |
| 25 | 4758911027946 |
| 26 | 17946417454046 |
| 27 | 67818937355227 |
| 28 | 256781370248500 |