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 | 6 |
| 2 | 24 |
| 3 | 90 |
| 4 | 336 |
| 5 | 1266 |
| 6 | 4824 |
| 7 | 18570 |
| 8 | 72096 |
| 9 | 281826 |
| 10 | 1107624 |
| 11 | 4371450 |
| 12 | 17308656 |
| 13 | 68703186 |
| 14 | 273218424 |
| 15 | 1088090730 |
| 16 | 4338014016 |
| 17 | 17309009346 |
| 18 | 69106897224 |
| 19 | 276040168410 |
| 20 | 1102998412176 |
| 21 | 4408506864306 |
| 22 | 17623567104024 |
| 23 | 70462887356490 |