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) |
|---|---|
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 5 |
| 6 | 20 |
| 7 | 74 |
| 8 | 263 |
| 9 | 914 |
| 10 | 3134 |
| 11 | 10655 |
| 12 | 36023 |
| 13 | 121331 |
| 14 | 407610 |
| 15 | 1366926 |
| 16 | 4578365 |
| 17 | 15321750 |
| 18 | 51245820 |
| 19 | 171335458 |
| 20 | 572714527 |
| 21 | 1914159445 |
| 22 | 6397373996 |
| 23 | 21381342737 |
| 24 | 71465609723 |
| 25 | 238892470728 |
| 26 | 798659461590 |
| 27 | 2670437231049 |
| 28 | 8930385538663 |
| 29 | 29869572490093 |
| 30 | 99922049387230 |
| 31 | 334324916304050 |