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 | 1 |
| 2 | 3 |
| 3 | 26 |
| 4 | 323 |
| 5 | 2415 |
| 6 | 26970 |
| 7 | 66526 |
| 8 | 717541 |
| 9 | 278992987 |
| 10 | 30741431 |
| 11 | 753069156 |
| 12 | 21291561634 |
| 13 | 1258540885373 |
| 14 | 11255629805034 |
| 15 | 833378477982 |
| 16 | 181778972767041 |
| 17 | 101220208716435 |
| 18 | 644821697046585 |
| 19 | 4759584409762049637 |
| 20 | 7692170694126370209 |
| 21 | 19898042621084590853 |