a(n) = 21*a(n-2) + 7*a(n-3), with a(0)=0, a(1)=3, and a(2)=6.

A215492

a(n) = 21*a(n-2) + 7*a(n-3), with a(0)=0, a(1)=3, and a(2)=6.

Terms

    a(0) =0a(1) =3a(2) =6a(3) =63a(4) =147a(5) =1365a(6) =3528a(7) =29694a(8) =83643a(9) =648270a(10) =1964361a(11) =14199171a(12) =45789471a(13) =311933118a(14) =1060973088a(15) =6871121775a(16) =24463966674a(17) =151720368891a(18) =561841152579

External references