a(n) = a(n-2) + 2^(n-1) + 5 for n>3, a(0..3) = (0,1,2,7).

Terms

a(0) =0a(1) =1a(2) =2a(3) =7a(4) =15a(5) =28a(6) =52a(7) =97a(8) =185a(9) =358a(10) =702a(11) =1387a(12) =2755a(13) =5488a(14) =10952a(15) =21877a(16) =43725a(17) =87418a(18) =174802a(19) =349567a(20) =699095a(21) =1398148a(22) =2796252a(23) =5592457a(24) =11184865a(25) =22369678a(26) =44739302a(27) =89478547a(28) =178957035a(29) =357914008