a(n) = Sum_{k=0..floor(4*n/7)} binomial(k,4*n-7*k).

Terms

a(0) =1a(1) =0a(2) =1a(3) =0a(4) =1a(5) =0a(6) =1a(7) =1a(8) =1a(9) =5a(10) =1a(11) =15a(12) =1a(13) =35a(14) =2a(15) =70a(16) =10a(17) =126a(18) =46a(19) =210a(20) =166a(21) =331a(22) =496a(23) =508a(24) =1288a(25) =806a(26) =3004a(27) =1456a(28) =6437a(29) =3185