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 | 5 |
| 2 | 25 |
| 3 | 120 |
| 4 | 570 |
| 5 | 2670 |
| 6 | 12380 |
| 7 | 56890 |
| 8 | 259445 |
| 9 | 1175355 |
| 10 | 5293671 |
| 11 | 23718780 |
| 12 | 105781845 |
| 13 | 469798125 |
| 14 | 2078552055 |
| 15 | 9164402118 |
| 16 | 40277785365 |
| 17 | 176503698495 |
| 18 | 771372344695 |
| 19 | 3362640467600 |
| 20 | 14624384170213 |
| 21 | 63463229049585 |
| 22 | 274836205944615 |