a(n) = A055450(n, n-4).

Terms

a(0) =1a(1) =5a(2) =14a(3) =28a(4) =42a(5) =174a(6) =735a(7) =3155a(8) =13726a(9) =60398a(10) =268361a(11) =1202425a(12) =5427110a(13) =24652698a(14) =112622124a(15) =517102008a(16) =2385026330a(17) =11045344150a(18) =51341255630a(19) =239447037890