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 | 454 |
| 8 | 1267 |
| 9 | 3613 |
| 10 | 10344 |
| 11 | 29572 |
| 12 | 84436 |
| 13 | 240868 |
| 14 | 686884 |
| 15 | 1959636 |
| 16 | 5592181 |
| 17 | 15957717 |
| 18 | 45533682 |
| 19 | 129922090 |
| 20 | 370708166 |
| 21 | 1057755082 |
| 22 | 3018154342 |
| 23 | 8611878218 |
| 24 | 24572725639 |
| 25 | 70114579881 |
| 26 | 200061418144 |
| 27 | 570845362600 |