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

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =1a(7) =1a(8) =2a(9) =9a(10) =37a(11) =121a(12) =331a(13) =793a(14) =1717a(15) =3433a(16) =6437a(17) =11456a(18) =19569a(19) =32505a(20) =53449a(21) =89149a(22) =155041a(23) =286825a(24) =564929a(25) =1163317a(26) =2442210a(27) =5117225a(28) =10558381a(29) =21308121