Number of 2n X 2n half-turn symmetric alternating-sign matrices (HTSASM's).

A059475

Number of 2n X 2n half-turn symmetric alternating-sign matrices (HTSASM's).

Terms

    a(0) =1a(1) =2a(2) =10a(3) =140a(4) =5544a(5) =622908a(6) =198846076a(7) =180473355920

External references