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 | 28 |
| 5 | 121 |
| 6 | 746 |
| 7 | 5041 |
| 8 | 40608 |
| 9 | 362936 |
| 10 | 3635017 |
| 11 | 39916801 |
| 12 | 479206146 |
| 13 | 6227020801 |
| 14 | 87187426839 |
| 15 | 1307674521272 |
| 16 | 20923334906117 |
| 17 | 355687428096001 |
| 18 | 6402415241245577 |
| 19 | 121645100408832001 |
| 20 | 2432905938909013343 |
| 21 | 51090942176372298027 |
| 22 | 1124001180562929946213 |