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 | 5 |
| 2 | 15 |
| 3 | 53 |
| 4 | 195 |
| 5 | 725 |
| 6 | 2703 |
| 7 | 10085 |
| 8 | 37635 |
| 9 | 140453 |
| 10 | 524175 |
| 11 | 1956245 |
| 12 | 7300803 |
| 13 | 27246965 |
| 14 | 101687055 |
| 15 | 379501253 |
| 16 | 1416317955 |
| 17 | 5285770565 |
| 18 | 19726764303 |
| 19 | 73621286645 |
| 20 | 274758382275 |
| 21 | 1025412242453 |
| 22 | 3826890587535 |
| 23 | 14282150107685 |
| 24 | 53301709843203 |
| 25 | 198924689265125 |
| 26 | 742397047217295 |
| 27 | 2770663499604053 |