a(n)=2^C(n,2)*(2(4^n-n*2^n)-1).A186941a(n)=2^C(n,2)*(2(4^n-n*2^n)-1).Terms a(0) =1a(1) =3a(2) =30a(3) =632a(4) =24512a(5) =1768448a(6) =243236864a(7) =64959283200External referencesoeis: A186941