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 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 21 |
| 5 | 55 |
| 6 | 151 |
| 7 | 447 |
| 8 | 1389 |
| 9 | 4502 |
| 10 | 15046 |
| 11 | 51505 |
| 12 | 179463 |
| 13 | 634086 |
| 14 | 2265014 |
| 15 | 8163125 |
| 16 | 29637903 |
| 17 | 108282989 |
| 18 | 397761507 |
| 19 | 1468063369 |
| 20 | 5441174511 |
| 21 | 20242989728 |
| 22 | 75566702558 |
| 23 | 282959337159 |
| 24 | 1062523000005 |
| 25 | 4000108867555 |
| 26 | 15095081362907 |
| 27 | 57088782570433 |