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 | 21 |
| 3 | 112 |
| 4 | 615 |
| 5 | 3432 |
| 6 | 19383 |
| 7 | 110448 |
| 8 | 633726 |
| 9 | 3656360 |
| 10 | 21191555 |
| 11 | 123286440 |
| 12 | 719539015 |
| 13 | 4210967880 |
| 14 | 24702429825 |
| 15 | 145210795200 |
| 16 | 855172338570 |
| 17 | 5044470461352 |
| 18 | 29799593861974 |
| 19 | 176268499363840 |
| 20 | 1043889366927771 |
| 21 | 6188748520285584 |
| 22 | 36726461258947569 |
| 23 | 218146172715259488 |
| 24 | 1296812014083995850 |