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 | 4 |
| 3 | 15 |
| 4 | 42 |
| 5 | 120 |
| 6 | 336 |
| 7 | 930 |
| 8 | 2548 |
| 9 | 6930 |
| 10 | 18870 |
| 11 | 51300 |
| 12 | 139440 |
| 13 | 379080 |
| 14 | 1030484 |
| 15 | 2801202 |
| 16 | 7614530 |
| 17 | 20698132 |
| 18 | 56264040 |
| 19 | 152941824 |
| 20 | 415739030 |
| 21 | 1130096128 |
| 22 | 3071920000 |
| 23 | 8350344420 |
| 24 | 22698590508 |
| 25 | 61701166395 |
| 26 | 167721158286 |
| 27 | 455913379324 |
| 28 | 1239301050624 |
| 29 | 3368769533514 |