a(n)=3*a(n-1)+12*a(n-2) for n>=3, a(0)=1, a(1)=3, a(2)=18 .

A133594

a(n)=3*a(n-1)+12*a(n-2) for n>=3, a(0)=1, a(1)=3, a(2)=18 .

Terms

    a(0) =1a(1) =3a(2) =18a(3) =90a(4) =486a(5) =2538a(6) =13446a(7) =70794a(8) =373734a(9) =1970730a(10) =10396998a(11) =54839754a(12) =289283238a(13) =1525926762a(14) =8049179142a(15) =42458658570a(16) =223966125414

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