a(n) = (10*2^n + 2*(-1)^n)/3 for n > 0; a(0) = 1.

Terms

a(0) =1a(1) =6a(2) =14a(3) =26a(4) =54a(5) =106a(6) =214a(7) =426a(8) =854a(9) =1706a(10) =3414a(11) =6826a(12) =13654a(13) =27306a(14) =54614a(15) =109226a(16) =218454a(17) =436906a(18) =873814a(19) =1747626a(20) =3495254a(21) =6990506a(22) =13981014a(23) =27962026a(24) =55924054a(25) =111848106a(26) =223696214a(27) =447392426a(28) =894784854a(29) =1789569706