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 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 7 |
| 6 | 23 |
| 7 | 71 |
| 8 | 255 |
| 9 | 911 |
| 10 | 3535 |
| 11 | 13903 |
| 12 | 57663 |
| 13 | 243871 |
| 14 | 1072031 |
| 15 | 4812575 |
| 16 | 22278399 |
| 17 | 105300287 |
| 18 | 510764095 |
| 19 | 2527547455 |
| 20 | 12794891007 |
| 21 | 66012404863 |
| 22 | 347599231103 |
| 23 | 1863520447103 |
| 24 | 10178746224639 |
| 25 | 56548686860543 |
| 26 | 319628408814847 |
| 27 | 1835814213846271 |