a(n) = Sum_{k=0..floor(2*n/7)} binomial(k+1,2*n-7*k).

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =2a(5) =0a(6) =0a(7) =1a(8) =3a(9) =0a(10) =0a(11) =4a(12) =4a(13) =0a(14) =1a(15) =10a(16) =5a(17) =0a(18) =6a(19) =20a(20) =6a(21) =1a(22) =21a(23) =35a(24) =7a(25) =8a(26) =56a(27) =56a(28) =9a(29) =36