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 | 12 |
| 3 | 53 |
| 4 | 252 |
| 5 | 1252 |
| 6 | 6416 |
| 7 | 33609 |
| 8 | 178996 |
| 9 | 965660 |
| 10 | 5263728 |
| 11 | 28936404 |
| 12 | 160204336 |
| 13 | 892313424 |
| 14 | 4995832640 |
| 15 | 28096475977 |
| 16 | 158638993476 |
| 17 | 898844200524 |
| 18 | 5108695394096 |
| 19 | 29117034808980 |
| 20 | 166370716319088 |
| 21 | 952789631705104 |
| 22 | 5467881256289856 |
| 23 | 31438798094242244 |
| 24 | 181079794531199440 |
| 25 | 1044651995141484912 |