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 | 3 |
| 2 | 15 |
| 3 | 60 |
| 4 | 260 |
| 5 | 1092 |
| 6 | 4641 |
| 7 | 19635 |
| 8 | 83215 |
| 9 | 352440 |
| 10 | 1493064 |
| 11 | 6324552 |
| 12 | 26791505 |
| 13 | 113490195 |
| 14 | 480752895 |
| 15 | 2036500788 |
| 16 | 8626757644 |
| 17 | 36543528780 |
| 18 | 154800876945 |
| 19 | 655747029795 |
| 20 | 2777789007071 |
| 21 | 11766903040368 |
| 22 | 49845401197200 |
| 23 | 211148507782800 |
| 24 | 894439432403425 |