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 | 1 |
| 2 | 4 |
| 3 | 9 |
| 4 | 40 |
| 5 | 120 |
| 6 | 570 |
| 7 | 1995 |
| 8 | 9898 |
| 9 | 38178 |
| 10 | 195216 |
| 11 | 805266 |
| 12 | 4209084 |
| 13 | 18239364 |
| 14 | 96941130 |
| 15 | 436235085 |
| 16 | 2349133930 |
| 17 | 10891439130 |
| 18 | 59272544760 |
| 19 | 281544587610 |
| 20 | 1545550116240 |
| 21 | 7489973640240 |
| 22 | 41416083787260 |
| 23 | 204122127237210 |
| 24 | 1135679731004700 |
| 25 | 5678398655023500 |
| 26 | 31760915181412800 |
| 27 | 160789633105902300 |