A089498 Duplicate of A046729.
0, 4, 20, 120, 696, 4060, 23660, 137904, 803760, 4684660, 27304196, 159140520
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.