90*A002451(n).

A213455

90*A002451(n).

Terms

    a(0) =90a(1) =1260a(2) =13230a(3) =126720a(4) =1171170a(5) =10663380a(6) =96461910a(7) =870123240a(8) =7838973450a(9) =70582218300a(10) =635365793790

External references