5196800domain: NAppears in sequencesTheta series of laminated lattice LAMBDA_12^{mid}.at n=13A006913Triangular array read by rows: T(n,k) is the number of f:{1,2,...,n}->{1,2,...,n} with exactly 2k elements that have a preimage of even (possibly zero) cardinality; n>=0, 0<=k<=floor(n/2).at n=23A225942