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 | 7 |
| 2 | 56 |
| 3 | 399 |
| 4 | 2800 |
| 5 | 19607 |
| 6 | 137256 |
| 7 | 960799 |
| 8 | 6725600 |
| 9 | 47079207 |
| 10 | 329554456 |
| 11 | 2306881199 |
| 12 | 16148168400 |
| 13 | 113037178807 |
| 14 | 791260251656 |
| 15 | 5538821761599 |
| 16 | 38771752331200 |
| 17 | 271402266318407 |
| 18 | 1899815864228856 |
| 19 | 13298711049601999 |
| 20 | 93090977347214000 |
| 21 | 651636841430498007 |