a(n) = 23 + floor( 1 + Sum_{j=1..n-1} a(j)/2 ).

Terms

a(0) =23a(1) =35a(2) =52a(3) =78a(4) =117a(5) =176a(6) =264a(7) =396a(8) =594a(9) =891a(10) =1336a(11) =2004a(12) =3006a(13) =4509a(14) =6764a(15) =10146a(16) =15219a(17) =22828a(18) =34242a(19) =51363a(20) =77045a(21) =115567a(22) =173351a(23) =260026a(24) =390039a(25) =585059a(26) =877588a(27) =1316382a(28) =1974573a(29) =2961860