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 | 5 |
| 3 | 31 |
| 4 | 245 |
| 5 | 2126 |
| 6 | 19811 |
| 7 | 192130 |
| 8 | 1922741 |
| 9 | 19692535 |
| 10 | 205446630 |
| 11 | 2175519380 |
| 12 | 23322657491 |
| 13 | 252631900236 |
| 14 | 2760768051914 |
| 15 | 30400169157656 |
| 16 | 336977765092789 |
| 17 | 3757141504436393 |
| 18 | 42107201595510563 |
| 19 | 474084628585822413 |
| 20 | 5359833704140820870 |
| 21 | 60823006052351729266 |