a(n) = 3*a(n-1) - 2*a(n-2) with a(0)=36 and a(1)=90.

Terms

a(0) =36a(1) =90a(2) =198a(3) =414a(4) =846a(5) =1710a(6) =3438a(7) =6894a(8) =13806a(9) =27630a(10) =55278a(11) =110574a(12) =221166a(13) =442350a(14) =884718a(15) =1769454a(16) =3538926a(17) =7077870a(18) =14155758a(19) =28311534a(20) =56623086a(21) =113246190a(22) =226492398a(23) =452984814a(24) =905969646a(25) =1811939310a(26) =3623878638a(27) =7247757294a(28) =14495514606a(29) =28991029230