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) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 18 |
| 4 | 112 |
| 5 | 953 |
| 6 | 10500 |
| 7 | 143308 |
| 8 | 2342284 |
| 9 | 44677494 |
| 10 | 974898636 |
| 11 | 23957348188 |
| 12 | 654735747960 |
| 13 | 19696461781336 |
| 14 | 646719936551000 |
| 15 | 23011823302544368 |
| 16 | 881974963187446672 |
| 17 | 36221318006594087010 |
| 18 | 1586737195260479665112 |
| 19 | 73850241923431162931872 |
| 20 | 3638980616346240786818936 |