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 | 39 |
| 3 | 141 |
| 4 | 587 |
| 5 | 2479 |
| 6 | 10731 |
| 7 | 47063 |
| 8 | 208547 |
| 9 | 931047 |
| 10 | 4180239 |
| 11 | 18849103 |
| 12 | 85269011 |
| 13 | 386687375 |
| 14 | 1756855951 |
| 15 | 7993210831 |
| 16 | 36405316227 |
| 17 | 165940691695 |
| 18 | 756832203759 |
| 19 | 3453347063599 |
| 20 | 15762537566627 |
| 21 | 71964915505967 |