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 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 7 |
| 4 | 23 |
| 5 | 71 |
| 6 | 251 |
| 7 | 883 |
| 8 | 3305 |
| 9 | 12505 |
| 10 | 48895 |
| 11 | 193755 |
| 12 | 783355 |
| 13 | 3205931 |
| 14 | 13302329 |
| 15 | 55764413 |
| 16 | 236174933 |
| 17 | 1008773269 |
| 18 | 4343533967 |
| 19 | 18834033443 |
| 20 | 82201462251 |
| 21 | 360883031291 |
| 22 | 1592993944723 |
| 23 | 7066748314147 |
| 24 | 31493800133173 |
| 25 | 140953938878821 |
| 26 | 633354801073571 |
| 27 | 2856369029213263 |