a(n) = 5*a(n-1) - 6*a(n-2) + a(n-3) with a(0)=1, a(1)=2, a(2)=7.

Terms

a(0) =1a(1) =2a(2) =7a(3) =24a(4) =80a(5) =263a(6) =859a(7) =2797a(8) =9094a(9) =29547a(10) =95968a(11) =311652a(12) =1011999a(13) =3286051a(14) =10669913a(15) =34645258a(16) =112492863a(17) =365262680a(18) =1186001480a(19) =3850924183a(20) =12503874715a(21) =40599829957a(22) =131826825678a(23) =428039023363