a(n) = T(2n+4,n), array T as in A055818.

Terms

a(0) =1a(1) =47a(2) =336a(3) =2128a(4) =12848a(5) =75808a(6) =441824a(7) =2557024a(8) =14737312a(9) =84726992a(10) =486388912a(11) =2789840688a(12) =15995087184a(13) =91689974592a(14) =525608606912