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 | 3 |
| 3 | 9 |
| 4 | 39 |
| 5 | 249 |
| 6 | 2559 |
| 7 | 5559 |
| 8 | 516069 |
| 9 | 10215759 |
| 10 | 233308629 |
| 11 | 6703001859 |
| 12 | 207263491989 |
| 13 | 7628001626799 |
| 14 | 311878265154009 |
| 15 | 13394639596824039 |
| 16 | 628284422185315449 |
| 17 | 33217442899375360179 |
| 18 | 1955977793053587999249 |