Forward difference of difference between 2^n and the next smaller power of 3.

Terms

a(0) =1a(1) =0a(2) =4a(3) =2a(4) =-2a(5) =32a(6) =10a(7) =-34a(8) =256a(9) =26a(10) =1024a(11) =590a(12) =-278a(13) =8192a(14) =3262a(15) =-6598a(16) =65536a(17) =12974a(18) =262144a(19) =169994a(20) =-14306a(21) =2097152a(22) =1005658a(23) =-1177330a(24) =16777216a(25) =4856618a(26) =-18984578a(27) =134217728a(28) =10155130a(29) =536870912