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 | 1 |
| 3 | 2 |
| 4 | 7 |
| 5 | 28 |
| 6 | 120 |
| 7 | 528 |
| 8 | 2344 |
| 9 | 10416 |
| 10 | 46160 |
| 11 | 203680 |
| 12 | 894312 |
| 13 | 3907056 |
| 14 | 16986352 |
| 15 | 73512288 |
| 16 | 316786960 |
| 17 | 1359763168 |
| 18 | 5815457184 |
| 19 | 24788842304 |
| 20 | 105340982248 |
| 21 | 446389242480 |
| 22 | 1886695382192 |
| 23 | 7955156287456 |
| 24 | 33468262290096 |
| 25 | 140516110684832 |
| 26 | 588832418973280 |
| 27 | 2463133441338048 |