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 | 9 |
| 2 | 18 |
| 3 | 36 |
| 4 | 81 |
| 5 | 180 |
| 6 | 405 |
| 7 | 918 |
| 8 | 2061 |
| 9 | 4635 |
| 10 | 10431 |
| 11 | 23472 |
| 12 | 52812 |
| 13 | 118827 |
| 14 | 267363 |
| 15 | 601560 |
| 16 | 1353510 |
| 17 | 3045402 |
| 18 | 6852150 |
| 19 | 15417342 |
| 20 | 34689015 |
| 21 | 78050286 |
| 22 | 175613148 |
| 23 | 395129583 |
| 24 | 889041555 |
| 25 | 2000343501 |
| 26 | 4500772875 |
| 27 | 10126738971 |
| 28 | 22785162687 |
| 29 | 51266616048 |
| 30 | 115349886108 |