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 | 9 |
| 2 | 69 |
| 3 | 531 |
| 4 | 4089 |
| 5 | 31491 |
| 6 | 242529 |
| 7 | 1867851 |
| 8 | 14385369 |
| 9 | 110789811 |
| 10 | 853254609 |
| 11 | 6571393371 |
| 12 | 50609994249 |
| 13 | 389776014531 |
| 14 | 3001884188289 |
| 15 | 23119197549291 |
| 16 | 178053936060729 |
| 17 | 1371293449053651 |
| 18 | 10561101680875569 |
| 19 | 81336980637343611 |
| 20 | 626421808927336809 |
| 21 | 4824426473972595171 |