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 | 0 |
| 2 | 2 |
| 3 | 4 |
| 4 | 10 |
| 5 | 28 |
| 6 | 84 |
| 7 | 264 |
| 8 | 858 |
| 9 | 2860 |
| 10 | 9724 |
| 11 | 33592 |
| 12 | 117572 |
| 13 | 416024 |
| 14 | 1485800 |
| 15 | 5348880 |
| 16 | 19389690 |
| 17 | 70715340 |
| 18 | 259289580 |
| 19 | 955277400 |
| 20 | 3534526380 |
| 21 | 13128240840 |
| 22 | 48932534040 |
| 23 | 182965127280 |
| 24 | 686119227300 |
| 25 | 2579808294648 |
| 26 | 9723892802904 |
| 27 | 36734706144304 |
| 28 | 139067101832008 |
| 29 | 527495903500720 |