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 | 0 |
| 1 | 4 |
| 2 | 12 |
| 3 | 44 |
| 4 | 172 |
| 5 | 2220 |
| 6 | 10412 |
| 7 | 141484 |
| 8 | 665772 |
| 9 | 9054380 |
| 10 | 545925292 |
| 11 | 2693408940 |
| 12 | 140132362412 |
| 13 | 2339155617964 |
| 14 | 11135248640172 |
| 15 | 151872736995500 |
| 16 | 9159071991736492 |
| 17 | 585619824295159980 |
| 18 | 2891462833508853932 |
| 19 | 150465415423185266860 |
| 20 | 2511648656858007873708 |