A161138 Main diagonal of the triangular array A161136.
1, 3, 9, 18, 80, 196, 554, 1824, 2292, 7218, 45522, 288135, 660113, 3201130, 10512530, 17675063, 191230544, 207521990
Offset: 1
Formula
a(m) = A161136(m,m).
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.