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 | 4 |
| 2 | 22 |
| 3 | 139 |
| 4 | 934 |
| 5 | 6484 |
| 6 | 45931 |
| 7 | 329893 |
| 8 | 2393470 |
| 9 | 17499892 |
| 10 | 128732992 |
| 11 | 951674398 |
| 12 | 7064138779 |
| 13 | 52616241370 |
| 14 | 393052285291 |
| 15 | 2943582912904 |
| 16 | 22093111508686 |
| 17 | 166141033332448 |
| 18 | 1251528633163264 |
| 19 | 9442096410241438 |
| 20 | 71333250226656784 |