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 | 4 |
| 2 | 18 |
| 3 | 90 |
| 4 | 494 |
| 5 | 2946 |
| 6 | 18926 |
| 7 | 130066 |
| 8 | 950654 |
| 9 | 7353794 |
| 10 | 59954638 |
| 11 | 513333618 |
| 12 | 4601380766 |
| 13 | 43062556322 |
| 14 | 419742815726 |
| 15 | 4252083713874 |
| 16 | 44680229906622 |
| 17 | 486145710591874 |
| 18 | 5468499473222670 |
| 19 | 63503107472489266 |
| 20 | 760281866742088670 |
| 21 | 9373065303624742498 |
| 22 | 118858898763010225198 |