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 | 3 |
| 2 | 9 |
| 3 | 18 |
| 4 | 54 |
| 5 | 72 |
| 6 | 405 |
| 7 | 390 |
| 8 | 1944 |
| 9 | 3411 |
| 10 | 14985 |
| 11 | 17802 |
| 12 | 139968 |
| 13 | 133104 |
| 14 | 798525 |
| 15 | 1804518 |
| 16 | 5454378 |
| 17 | 8072532 |
| 18 | 64599849 |
| 19 | 64573626 |
| 20 | 437732424 |
| 21 | 872157294 |
| 22 | 3138159429 |
| 23 | 4279259574 |
| 24 | 35362084140 |
| 25 | 42364514403 |
| 26 | 211822562025 |
| 27 | 423646166250 |