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 | 12 |
| 3 | 56 |
| 4 | 244 |
| 5 | 1396 |
| 6 | 8200 |
| 7 | 55092 |
| 8 | 390216 |
| 9 | 3005288 |
| 10 | 24571056 |
| 11 | 212258216 |
| 12 | 1939879668 |
| 13 | 18429618408 |
| 14 | 184041761768 |
| 15 | 1891831332208 |
| 16 | 20301171282452 |
| 17 | 222742563853912 |
| 18 | 2534535926617852 |
| 19 | 29335558770589276 |
| 20 | 349980362625040712 |
| 21 | 4228388321175157140 |