a(n) = 4*a(n-1) - 4*a(n-2) + 4*a(n-3) with a(0) = 1, a(1) = 3, a(2) = 10.

Terms

a(0) =1a(1) =3a(2) =10a(3) =32a(4) =100a(5) =312a(6) =976a(7) =3056a(8) =9568a(9) =29952a(10) =93760a(11) =293504a(12) =918784a(13) =2876160a(14) =9003520a(15) =28184576a(16) =88228864a(17) =276191232a(18) =864587776a(19) =2706501632a(20) =8472420352a(21) =26522025984a(22) =83024429056a(23) =259899293696a(24) =813587562496