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 | 2 |
| 2 | 6 |
| 3 | 26 |
| 4 | 148 |
| 5 | 1032 |
| 6 | 8464 |
| 7 | 79592 |
| 8 | 842832 |
| 9 | 9914336 |
| 10 | 128162464 |
| 11 | 1804852128 |
| 12 | 27489582784 |
| 13 | 450089665664 |
| 14 | 7880963503872 |
| 15 | 146913179393408 |
| 16 | 2904309329449216 |
| 17 | 60677563647195648 |
| 18 | 1335634021282590208 |
| 19 | 30891084696208976384 |
| 20 | 748854186528315687936 |