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 | 24 |
| 3 | 170 |
| 4 | 1320 |
| 5 | 10868 |
| 6 | 93199 |
| 7 | 823548 |
| 8 | 7446480 |
| 9 | 68567202 |
| 10 | 640757920 |
| 11 | 6061477500 |
| 12 | 57933260067 |
| 13 | 558580920160 |
| 14 | 5426644737984 |
| 15 | 53069206438226 |
| 16 | 522004849765080 |
| 17 | 5161083186971000 |
| 18 | 51262685633583970 |
| 19 | 511272660117154692 |
| 20 | 5118240198221249088 |