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 | 13 |
| 3 | 74 |
| 4 | 499 |
| 5 | 3719 |
| 6 | 29494 |
| 7 | 243888 |
| 8 | 2078431 |
| 9 | 18122369 |
| 10 | 160885449 |
| 11 | 1449268478 |
| 12 | 13213370392 |
| 13 | 121696581804 |
| 14 | 1130565483472 |
| 15 | 10581614352704 |
| 16 | 99685591788687 |
| 17 | 944490400760597 |
| 18 | 8994266558594671 |
| 19 | 86040075341770806 |
| 20 | 826423263373253923 |
| 21 | 7967095415955791687 |