Variant on Lucas numbers: a(n) = a(n-1) + 3*a(n-2) with a(0)=2 and a(1)=1.

Terms

a(0) =2a(1) =1a(2) =7a(3) =10a(4) =31a(5) =61a(6) =154a(7) =337a(8) =799a(9) =1810a(10) =4207a(11) =9637a(12) =22258a(13) =51169a(14) =117943a(15) =271450a(16) =625279a(17) =1439629a(18) =3315466a(19) =7634353a(20) =17580751a(21) =40483810a(22) =93226063a(23) =214677493a(24) =494355682a(25) =1138388161a(26) =2621455207a(27) =6036619690a(28) =13900985311a(29) =32010844381