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 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 45 |
| 5 | 151 |
| 6 | 483 |
| 7 | 1513 |
| 8 | 4665 |
| 9 | 14251 |
| 10 | 43263 |
| 11 | 130813 |
| 12 | 394485 |
| 13 | 1187551 |
| 14 | 3570843 |
| 15 | 10728913 |
| 16 | 32219505 |
| 17 | 96724051 |
| 18 | 290303223 |
| 19 | 871171813 |
| 20 | 2614039725 |
| 21 | 7843167751 |
| 22 | 23531600403 |
| 23 | 70598995513 |
| 24 | 211805375145 |
| 25 | 635432902651 |