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 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 25 |
| 6 | 75 |
| 7 | 231 |
| 8 | 763 |
| 9 | 2619 |
| 10 | 9495 |
| 11 | 35695 |
| 12 | 140151 |
| 13 | 568503 |
| 14 | 2390479 |
| 15 | 10349535 |
| 16 | 46206735 |
| 17 | 211799311 |
| 18 | 997313823 |
| 19 | 4809701439 |
| 20 | 23758664095 |
| 21 | 119952692895 |
| 22 | 618884638911 |
| 23 | 3257843882623 |
| 24 | 17492190577599 |
| 25 | 95680443760575 |
| 26 | 532985208200575 |
| 27 | 3020676745975551 |