A027321 Duplicate of A027315.
1, 2, 6, 20, 90, 692, 5774, 48924, 417440, 3580036, 30831756, 266463804
Offset: 0
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.