A hierarchical sequence (S(W3{2,2}*cc) - see A059126).

Terms

a(0) =15a(1) =54a(2) =141a(3) =324a(4) =699a(5) =1458a(6) =2985a(7) =6048a(8) =12183a(9) =24462a(10) =49029a(11) =98172a(12) =196467a(13) =393066a(14) =786273a(15) =1572696a(16) =3145551a(17) =6291270a(18) =12582717a(19) =25165620a(20) =50331435a(21) =100663074a(22) =201326361a(23) =402652944a(24) =805306119a(25) =1610612478a(26) =3221225205a(27) =6442450668a(28) =12884901603a(29) =25769803482