a(n) = 318*2^n - 186 (n>=1).

Terms

a(0) =450a(1) =1086a(2) =2358a(3) =4902a(4) =9990a(5) =20166a(6) =40518a(7) =81222a(8) =162630a(9) =325446a(10) =651078a(11) =1302342a(12) =2604870a(13) =5209926a(14) =10420038a(15) =20840262a(16) =41680710a(17) =83361606a(18) =166723398a(19) =333446982a(20) =666894150a(21) =1333788486a(22) =2667577158a(23) =5335154502a(24) =10670309190a(25) =21340618566a(26) =42681237318a(27) =85362474822a(28) =170724949830a(29) =341449899846