a(n) = Sum_{k=0..n} k^4 * (-1)^k * 3^(n-k) * binomial(n,k).

Terms

a(0) =0a(1) =-1a(2) =10a(3) =36a(4) =40a(5) =-160a(6) =-1152a(7) =-4480a(8) =-13568a(9) =-34560a(10) =-74240a(11) =-123904a(12) =-92160a(13) =425984a(14) =2867200a(15) =11796480a(16) =40763392a(17) =128122880a(18) =378667008a(19) =1070858240a(20) =2928148480a(21) =7795113984a(22) =20300431360a(23) =51900317696a(24) =130610626560a(25) =324219699200a(26) =795206483968