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 | 0 |
| 1 | 0 |
| 2 | 6 |
| 3 | 36 |
| 4 | 132 |
| 5 | 540 |
| 6 | 2076 |
| 7 | 8316 |
| 8 | 32892 |
| 9 | 131580 |
| 10 | 524796 |
| 11 | 2099196 |
| 12 | 8390652 |
| 13 | 33562620 |
| 14 | 134225916 |
| 15 | 536903676 |
| 16 | 2147516412 |
| 17 | 8590065660 |
| 18 | 34359869436 |
| 19 | 137439477756 |
| 20 | 549756338172 |
| 21 | 2199025352700 |
| 22 | 8796095119356 |
| 23 | 35184380477436 |
| 24 | 140737496743932 |