a(n) = (-3 - 28*3^n + 73*15^n)/21.

A260846

a(n) = (-3 - 28*3^n + 73*15^n)/21.

Terms

    a(0) =2a(1) =48a(2) =770a(3) =11696a(4) =175874a(5) =2639408a(6) =39595010a(7) =593936816a(8) =8909087234a(9) =133636413488

External references