a(n) is the hafnian of the 2n X 2n symmetric matrix defined by M[i,j] = i*j - ceiling(i*j/3).

A358164

a(n) is the hafnian of the 2n X 2n symmetric matrix defined by M[i,j] = i*j - ceiling(i*j/3).

Terms

    a(0) =1a(1) =1a(2) =26a(3) =2704a(4) =698568a(5) =384890688a(6) =378771904512

External references