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 | 55 |
| 4 | 315 |
| 5 | 2106 |
| 6 | 15946 |
| 7 | 134730 |
| 8 | 1253637 |
| 9 | 12702961 |
| 10 | 138955146 |
| 11 | 1629581955 |
| 12 | 20371061009 |
| 13 | 270124999977 |
| 14 | 3783651174906 |
| 15 | 55780472480036 |
| 16 | 862795543656489 |
| 17 | 13963065117796548 |
| 18 | 235845816764772718 |
| 19 | 4148499020022749151 |
| 20 | 75841424406989195136 |