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 | 6 |
| 2 | 18 |
| 3 | 60 |
| 4 | 210 |
| 5 | 756 |
| 6 | 2772 |
| 7 | 10296 |
| 8 | 38610 |
| 9 | 145860 |
| 10 | 554268 |
| 11 | 2116296 |
| 12 | 8112468 |
| 13 | 31201800 |
| 14 | 120349800 |
| 15 | 465352560 |
| 16 | 1803241170 |
| 17 | 7000818660 |
| 18 | 27225405900 |
| 19 | 106035791400 |
| 20 | 413539586460 |
| 21 | 1614773623320 |
| 22 | 6312296891160 |
| 23 | 24700292182800 |
| 24 | 96742811049300 |
| 25 | 379231819313256 |