a(n) = 11*2^n - 1.

Terms

a(0) =10a(1) =21a(2) =43a(3) =87a(4) =175a(5) =351a(6) =703a(7) =1407a(8) =2815a(9) =5631a(10) =11263a(11) =22527a(12) =45055a(13) =90111a(14) =180223a(15) =360447a(16) =720895a(17) =1441791a(18) =2883583a(19) =5767167a(20) =11534335a(21) =23068671a(22) =46137343a(23) =92274687a(24) =184549375a(25) =369098751a(26) =738197503a(27) =1476395007a(28) =2952790015