a(n) = binomial(n, floor(n/4)).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =4a(5) =5a(6) =6a(7) =7a(8) =28a(9) =36a(10) =45a(11) =55a(12) =220a(13) =286a(14) =364a(15) =455a(16) =1820a(17) =2380a(18) =3060a(19) =3876a(20) =15504a(21) =20349a(22) =26334a(23) =33649a(24) =134596a(25) =177100a(26) =230230a(27) =296010a(28) =1184040a(29) =1560780