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 | 3 |
| 2 | 15 |
| 3 | 91 |
| 4 | 613 |
| 5 | 4410 |
| 6 | 33190 |
| 7 | 258129 |
| 8 | 2058281 |
| 9 | 16737259 |
| 10 | 138268611 |
| 11 | 1157197639 |
| 12 | 9790774861 |
| 13 | 83606543660 |
| 14 | 719638883748 |
| 15 | 6237175439640 |
| 16 | 54386540912490 |
| 17 | 476782443732437 |
| 18 | 4199713449255749 |
| 19 | 37151346765537606 |
| 20 | 329914740292813170 |
| 21 | 2939975733035070000 |