Let x(1)=1, x(n+1) = (4/3)*x(n) - floor((4/3)*x(n)); then a(n)=x(n)*3^n.

Terms

a(0) =1a(1) =4a(2) =16a(3) =64a(4) =13a(5) =52a(6) =208a(7) =832a(8) =3328a(9) =13312a(10) =53248a(11) =212992a(12) =851968a(13) =3407872a(14) =13631488a(15) =11479231a(16) =45916924a(17) =183667696a(18) =734670784a(19) =2938683136a(20) =1294379341a(21) =5177517364a(22) =20710069456a(23) =82840277824a(24) =331361111296