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 | 2 |
| 3 | 6 |
| 4 | 22 |
| 5 | 84 |
| 6 | 320 |
| 7 | 1212 |
| 8 | 4576 |
| 9 | 17256 |
| 10 | 65048 |
| 11 | 245184 |
| 12 | 924160 |
| 13 | 3483408 |
| 14 | 13129952 |
| 15 | 49490592 |
| 16 | 186544480 |
| 17 | 703140672 |
| 18 | 2650342784 |
| 19 | 9989916864 |
| 20 | 37654917376 |
| 21 | 141932392320 |
| 22 | 534984681344 |
| 23 | 2016513669120 |
| 24 | 7600829555200 |
| 25 | 28649748728064 |
| 26 | 107989278831104 |
| 27 | 407043163037184 |