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 | 2 |
| 2 | 6 |
| 3 | 18 |
| 4 | 54 |
| 5 | 172 |
| 6 | 564 |
| 7 | 1900 |
| 8 | 6542 |
| 9 | 23000 |
| 10 | 82025 |
| 11 | 295947 |
| 12 | 1077871 |
| 13 | 3957809 |
| 14 | 14630843 |
| 15 | 54400028 |
| 16 | 203280221 |
| 17 | 762939111 |
| 18 | 2874398515 |
| 19 | 10866266172 |
| 20 | 41203088796 |
| 21 | 156661034233 |
| 22 | 597116381732 |
| 23 | 2280998753949 |
| 24 | 8731188863470 |
| 25 | 33483379603407 |
| 26 | 128625503610475 |
| 27 | 494890204904784 |