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 | 2 |
| 2 | 14 |
| 3 | 112 |
| 4 | 910 |
| 5 | 8008 |
| 6 | 84588 |
| 7 | 1059296 |
| 8 | 13998070 |
| 9 | 179505848 |
| 10 | 2193386772 |
| 11 | 26007310560 |
| 12 | 306461781228 |
| 13 | 3616653947520 |
| 14 | 42388643986040 |
| 15 | 493154764709376 |
| 16 | 5905712543971814 |
| 17 | 78382075059128216 |
| 18 | 1209853310234969668 |
| 19 | 20945651586098921696 |
| 20 | 378625571347575985092 |