a(n) = (6^n+2^n-2*3^n)*(n-1)!/2.

A381219

a(n) = (6^n+2^n-2*3^n)*(n-1)!/2.

Terms

    a(0) =1a(1) =11a(2) =170a(3) =3450a(4) =87864a(5) =2715720a(6) =99248400a(7) =4200210000a(8) =202383054720

External references