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 | 0 |
| 1 | 1 |
| 2 | 7 |
| 3 | 40 |
| 4 | 217 |
| 5 | 1156 |
| 6 | 6097 |
| 7 | 31900 |
| 8 | 165697 |
| 9 | 855076 |
| 10 | 4387537 |
| 11 | 22404460 |
| 12 | 113945377 |
| 13 | 577590196 |
| 14 | 2919923377 |
| 15 | 14729076220 |
| 16 | 74167952257 |
| 17 | 372944296516 |
| 18 | 1873182473617 |
| 19 | 9399885079180 |
| 20 | 47135702874337 |
| 21 | 236224784974036 |