a(n) = a(n-1) - a(n-2) if n is prime or a(n-1) + a(n-2) otherwise. a(1) = a(2) = 1.

Terms

a(0) =1a(1) =1a(2) =0a(3) =1a(4) =1a(5) =2a(6) =1a(7) =3a(8) =4a(9) =7a(10) =3a(11) =10a(12) =7a(13) =17a(14) =24a(15) =41a(16) =17a(17) =58a(18) =41a(19) =99a(20) =140a(21) =239a(22) =99a(23) =338a(24) =437a(25) =775a(26) =1212a(27) =1987a(28) =775a(29) =2762