a(n) = T(n, 2*n-8), T given by A027960.

Terms

a(0) =1a(1) =4a(2) =11a(3) =29a(4) =76a(5) =196a(6) =487a(7) =1148a(8) =2552a(9) =5353a(10) =10636a(11) =20120a(12) =36425a(13) =63415a(14) =106630a(15) =173821a(16) =275603a(17) =426242a(18) =644593a(19) =955207a(20) =1389626a(21) =1987886a(22) =2800249a(23) =3889186a(24) =5331634a(25) =7221551a(26) =9672794a(27) =12822346a(28) =16833919a(29) =21901961