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 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 37 |
| 6 | 130 |
| 7 | 428 |
| 8 | 1481 |
| 9 | 5091 |
| 10 | 17979 |
| 11 | 64176 |
| 12 | 234311 |
| 13 | 869645 |
| 14 | 3295100 |
| 15 | 12720494 |
| 16 | 50083996 |
| 17 | 200964437 |
| 18 | 821845766 |
| 19 | 3423694821 |
| 20 | 14524845181 |
| 21 | 62725701708 |
| 22 | 275629610199 |
| 23 | 1231863834775 |
| 24 | 5597240308384 |
| 25 | 25844969339979 |
| 26 | 121224757935416 |
| 27 | 577359833539428 |
| 28 | 2791096628891679 |