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 | 7 |
| 2 | 35 |
| 3 | 147 |
| 4 | 553 |
| 5 | 1925 |
| 6 | 6321 |
| 7 | 19825 |
| 8 | 59906 |
| 9 | 175504 |
| 10 | 500864 |
| 11 | 1397536 |
| 12 | 3823680 |
| 13 | 10282496 |
| 14 | 27230464 |
| 15 | 71129856 |
| 16 | 183518720 |
| 17 | 468213760 |
| 18 | 1182433280 |
| 19 | 2958376960 |
| 20 | 7338426368 |
| 21 | 18059821056 |
| 22 | 44120473600 |
| 23 | 107055742976 |
| 24 | 258122317824 |
| 25 | 618683957248 |
| 26 | 1474700509184 |