a(n) = Sum_{k=0..floor(n/7)} C(n-5*k,2*k).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =1a(7) =2a(8) =4a(9) =7a(10) =11a(11) =16a(12) =22a(13) =29a(14) =38a(15) =51a(16) =71a(17) =102a(18) =149a(19) =218a(20) =316a(21) =452a(22) =639a(23) =897a(24) =1257a(25) =1766a(26) =2493a(27) =3536a(28) =5031a(29) =7165