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) |
|---|---|
| 0 | 2 |
| 1 | 4 |
| 2 | 12 |
| 3 | 40 |
| 4 | 136 |
| 5 | 464 |
| 6 | 1584 |
| 7 | 5408 |
| 8 | 18464 |
| 9 | 63040 |
| 10 | 215232 |
| 11 | 734848 |
| 12 | 2508928 |
| 13 | 8566016 |
| 14 | 29246208 |
| 15 | 99852800 |
| 16 | 340918784 |
| 17 | 1163969536 |
| 18 | 3974040576 |
| 19 | 13568223232 |
| 20 | 46324811776 |
| 21 | 158162800640 |
| 22 | 540001579008 |
| 23 | 1843680714752 |
| 24 | 6294719700992 |