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 | 2 |
| 2 | 6 |
| 3 | 21 |
| 4 | 75 |
| 5 | 273 |
| 6 | 1008 |
| 7 | 3762 |
| 8 | 14158 |
| 9 | 53635 |
| 10 | 204270 |
| 11 | 781378 |
| 12 | 2999906 |
| 13 | 11553234 |
| 14 | 44612760 |
| 15 | 172671925 |
| 16 | 669679793 |
| 17 | 2601913466 |
| 18 | 10125418060 |
| 19 | 39459828905 |
| 20 | 153977743500 |
| 21 | 601545298200 |
| 22 | 2352559491900 |
| 23 | 9209476821105 |
| 24 | 36084150102001 |
| 25 | 141499349638556 |
| 26 | 555292275455022 |
| 27 | 2180689496523468 |
| 28 | 8569380062230708 |