A symmetrical triangle sequence: T(n, k) = q^k + q^(n-k) - q^n, with q=4.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =-8a(5) =1a(6) =1a(7) =-44a(8) =-44a(9) =1a(10) =1a(11) =-188a(12) =-224a(13) =-188a(14) =1a(15) =1a(16) =-764a(17) =-944a(18) =-944a(19) =-764a(20) =1a(21) =1a(22) =-3068a(23) =-3824a(24) =-3968a(25) =-3824a(26) =-3068a(27) =1a(28) =1a(29) =-12284