a(n) = 13*2^n.

Terms

a(0) =13a(1) =26a(2) =52a(3) =104a(4) =208a(5) =416a(6) =832a(7) =1664a(8) =3328a(9) =6656a(10) =13312a(11) =26624a(12) =53248a(13) =106496a(14) =212992a(15) =425984a(16) =851968a(17) =1703936a(18) =3407872a(19) =6815744a(20) =13631488a(21) =27262976a(22) =54525952a(23) =109051904a(24) =218103808a(25) =436207616a(26) =872415232a(27) =1744830464a(28) =3489660928a(29) =6979321856