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 | 13 |
| 4 | 69 |
| 5 | 457 |
| 6 | 3579 |
| 7 | 32521 |
| 8 | 335853 |
| 9 | 3888823 |
| 10 | 49902045 |
| 11 | 703123621 |
| 12 | 10793341131 |
| 13 | 179315984983 |
| 14 | 3205886624445 |
| 15 | 61375996359973 |
| 16 | 1252826360392317 |
| 17 | 27162281897430607 |
| 18 | 623375610559904343 |
| 19 | 15098095476369328345 |
| 20 | 384854289897145441635 |
| 21 | 10299091666341922887571 |