a(n) = 11*4^n - 1.

Terms

a(0) =10a(1) =43a(2) =175a(3) =703a(4) =2815a(5) =11263a(6) =45055a(7) =180223a(8) =720895a(9) =2883583a(10) =11534335a(11) =46137343a(12) =184549375a(13) =738197503a(14) =2952790015a(15) =11811160063a(16) =47244640255a(17) =188978561023a(18) =755914244095