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 | 0 |
| 1 | 5 |
| 2 | 55 |
| 3 | 485 |
| 4 | 4015 |
| 5 | 32525 |
| 6 | 261415 |
| 7 | 2094965 |
| 8 | 16770655 |
| 9 | 134198045 |
| 10 | 1073682775 |
| 11 | 8589757445 |
| 12 | 68718945295 |
| 13 | 549754219565 |
| 14 | 4398041728135 |
| 15 | 35184357739925 |
| 16 | 281474933663935 |
| 17 | 2251799684545085 |
| 18 | 18014398122061495 |
| 19 | 144115186913594405 |
| 20 | 1152921501120062575 |
| 21 | 9223372026394422605 |