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 | 0 |
| 2 | 1 |
| 3 | 5 |
| 4 | 33 |
| 5 | 193 |
| 6 | 1169 |
| 7 | 6993 |
| 8 | 42001 |
| 9 | 251921 |
| 10 | 1511697 |
| 11 | 9069841 |
| 12 | 54419729 |
| 13 | 326517009 |
| 14 | 1959104785 |
| 15 | 11754623249 |
| 16 | 70527750417 |
| 17 | 423166480657 |
| 18 | 2538998927633 |
| 19 | 15233993478417 |
| 20 | 91403961045265 |
| 21 | 548423765922065 |