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 | 6 |
| 4 | 18 |
| 5 | 54 |
| 6 | 162 |
| 7 | 486 |
| 8 | 1394 |
| 9 | 3991 |
| 10 | 11593 |
| 11 | 33772 |
| 12 | 98320 |
| 13 | 286072 |
| 14 | 831952 |
| 15 | 2418664 |
| 16 | 7030816 |
| 17 | 20441944 |
| 18 | 59441521 |
| 19 | 172843609 |
| 20 | 502580846 |
| 21 | 1461344622 |
| 22 | 4249102850 |
| 23 | 12354982862 |
| 24 | 35924300898 |
| 25 | 104456501102 |
| 26 | 303726483778 |
| 27 | 883140022543 |