Triangle, read by rows, T(n,k) = (-1)^k*binomial(n, k)*3^(n-k).

Terms

a(0) =1a(1) =3a(2) =-1a(3) =9a(4) =-6a(5) =1a(6) =27a(7) =-27a(8) =9a(9) =-1a(10) =81a(11) =-108a(12) =54a(13) =-12a(14) =1a(15) =243a(16) =-405a(17) =270a(18) =-90a(19) =15a(20) =-1a(21) =729a(22) =-1458a(23) =1215a(24) =-540a(25) =135a(26) =-18a(27) =1a(28) =2187a(29) =-5103